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Baby Mermaid Costume Crochet Pattern

Baby Mermaid Costume Crochet Pattern
4.5★ Rating
5-7 Hours Time Needed
1.4K Made This
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Intermediate Level

Ideal for those with basic crochet experience, featuring slightly more advanced stitches and techniques to expand your skills.

⏱️

Weekend Treat

Takes 5-7 hours, making it an enjoyable project to finish over a couple of days.

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Snug Essential

Everyday comfort with practical charm, designed for both functionality and style through changing seasons.

About This Baby Mermaid Costume Crochet Pattern

This pattern creates a sweet baby mermaid costume set with a crochet tail, fin/flippers, a choice of shell or starfish bikini tops, and a coordinating headband. It includes scalloped and shell edge details, optional scales, and assembly instructions so you can finish a polished costume. The design is adaptable for different yarns and hook sizes so you can adjust fit and texture.

Baby Mermaid Costume Crochet Pattern crochet pattern - detailed view of completed project

You will work common stitches like DC, HDC, and shell stitches with tips for shaping and joining. The instructions include how to make the tail, attach flippers, make starfish, and add a wavy scale trim for a finished look.

Why You'll Love This Baby Mermaid Costume Crochet Pattern

I absolutely love this pattern because it turns simple stitches into a whimsical costume that photographs beautifully and feels special to gift. I enjoy how the scalloped edge and shell details add instant charm with very little extra work. I love that it is adjustable — you can change yarn weight and hook size to make tiny newborn sizes or larger 3-6 month versions. I also enjoy sewing on the flippers and watching the tail transform as the gathers create a realistic mermaid silhouette. Making starfish and adding pearls is my favorite finishing touch because it gives a delightful handmade sparkle.

Baby Mermaid Costume Crochet Pattern step 1 - construction progress Baby Mermaid Costume Crochet Pattern step 2 - assembly progress Baby Mermaid Costume Crochet Pattern step 3 - details and accessories Baby Mermaid Costume Crochet Pattern step 4 - final assembly and finishing

Switch Things Up

I love customizing this pattern by changing yarn colors and textures to create very different looks; try pastel ombre yarn for a soft newborn aesthetic or bright neon for a playful splash.

I often adjust size by changing hooks and yarn weight: using bulky yarn with a larger hook makes a chunkier, cozier tail while using thinner yarn and smaller hooks creates tiny, delicate versions perfect for newborn photo props.

I like adding embroidery, beads, or felt accents to the starfish centers for extra personality; sewing small pearls into the starfish creates a vintage or princess look.

Try different shell stitch patterns for the scalloped edge to vary the scale size; you can work fewer or more double crochets per shell to make larger or smaller scallops.

I sometimes add a thin wire inside the fin seam for posability — this lets the fin hold a slightly shaped curve for display, but make sure any wire ends are wrapped and secured safely away from the baby.

For a photo-ready finish, I switch up the tie cord style: a braided chain rope looks neat and holds securely, while a long decorative chain can be tied in a bow at the back for extra charm.

I recommend experimenting with contrast trim for the scales: a sparkly or metallic accent yarn creates a shimmery effect that catches light in photos.

If you want a two-piece mermaid set, I sometimes make two shorter tails and add detachable belts so the tail can be removed quickly between shots or diaper changes.

I also suggest creating a coordinating hat or bonnet in the same yarn to complete the set; a simple shell-stitch band on a newborn hat ties the look together beautifully.

Finally, I recommend practicing starfish and shell cups on scrap yarn first to dial in your tension and achieve consistent size across pieces before attaching them to the main costume.

Common Mistakes & How to Fix Them

✗ Skipping the slip stitch join at the end of the round; always join with a slip stitch to the first dc to maintain an even seam and consistent stitch count. ✗ Working too loosely on increases which causes a floppy tail; keep a consistent, moderately tight tension especially on rounds where you increase stitch count to maintain shape. ✗ Cutting gathering strings before sewing flippers in place; leave the gather strings until you have completely sewn the flippers so you can adjust the fit and alignment. ✗ Not counting stitches after increase or decrease rounds; count after each increase/decrease round to ensure your stitch total matches the pattern and to avoid reconstructing rows later. ✗ Placing shell scallops too close to the top edge causing a bulky finish; join scalloped trim slightly lower and work loosely so the scalloped edge lays nicely without pulling.

Baby Mermaid Costume Crochet Pattern

Create an adorable baby mermaid costume including a textured tail, scalloped fin edges, removable flippers, a bikini band or shell top, headband and starfish accents. This pattern walks you through each section with clear step-by-step instructions so you can customize size and color. Perfect for photoshoots, gifts, or a whimsical handmade outfit for a little one.

Intermediate 5-7 Hours

Materials Needed for Baby Mermaid Costume Crochet Pattern

— Main Fabric

  • 01
    4WW (medium) yarn (also called worsted weight, #4) - main color for tail (amount depends on size, approx 150-300g for baby sizes)
  • 02
    Red Heart Super Saver (example used) - any color for tail and fins
  • 03
    Love This Yarn (Bernat type) as an alternative for similar weight and softer feel
  • 04
    Simply Soft (lighter texture) can be used for a smaller newborn tail when using K hook for tail
  • 05
    Accent yarn for scallops, scales, starfish, and bikini band - small amounts (20-50g each)
  • 06
    Contrasting yarn for scale trim (optional)

— Tools Required

  • 01
    Crochet hook size I (5.5mm) for tail (suggested)
  • 02
    Crochet hook size K (6.5mm) for tail fins or alternate sizing
  • 03
    Crochet hook size J (6.0mm) optional for fins
  • 04
    Crochet hook size H (5.0mm) for bikini band, headband, scales and starfish
  • 05
    Yarn needle for sewing and weaving ends
  • 06
    Ruler or measuring tape
  • 07
    Scissors
  • 08
    Pins for assembly and positioning flippers
  • 09
    Buttons (1-2) for bikini band closure and headband closure
  • 10
    Small pearls or beads (about 9 per large starfish) for decoration
  • 11
    Stitch markers (optional) to mark rounds

Progress Tracker

0% Complete

— Tail :

Info :

TAIL: Use I hook (Red Heart or Love This Yarn) 14" approx from top to bottom of tail-fins not included.

Info :

*At the end of each sentence, a notation of how many DC you should have is listed. If you do not have this amount, rip out the row and start over so that the pattern comes out correctly in the end.

Round 1 :

Magic circle, ch2, 6 dc in circle, joins with sl st into 1st dc. Tighten circle so there is not hole showing. 6dc. (At this point you should have what looks like a tiny cup)

Round 2 :

Ch 2, *1dc in 1st st, 2 dc in next st. Repeat from * around. Join w sl st in 1st dc. 9 dc(keep your stitches snug, but not too tight, you are building the base of the tail). You should have something that looks like this:

Round 3 :

Ch2, *1dc, in next 2 sts, 2 dc in next st. Repeat from * around. Join with sl st in 1st dc. 12 dc

Round 4 :

Ch2, *1dc in next 2 sts, 2 dc in next st. Repeat from * around. Join w sl st in 1st dc. 16 dc

Round 5 :

Ch 2, 1dc in each st around. Join w sl st in 1st dc. 16 dc

Round 6 :

Ch 2,*1dc in next 3 sts, 2 dc in next. Repeat from * around. Join w sl st in 1st dc. 20 dc

Round 7 :

Ch 2, 1dc in each st around. Join w sl st in first dc. 20 dc

Round 8 :

Ch2, *1dc in next 4 sts, 2 dc in next st. Repeat from * around. Join with sl st in 1st dc. 24 dc

Round 9 :

Ch 2, 1 dc in each st around. Join w sl st in first dc. 24 dc

Round 10 :

Ch 2, 1 dc in each st around. Join w sl st in 1st dc. 24 dc

Round 11 :

Ch2, * 1 dc in next 5 sts, 2 dc in next st. Repeat from * around. Join w sl st in 1st dc. 28 dc

Round 12 :

Ch 2, 1 dc in each st around. Join w sl st in 1st dc. 28 dc

Round 13 :

Ch 2, * 1 dc in next 3 stst, 2 dc in next st. Join w sl st in 1st dc. 35 dc.

Round 14 :

Ch 2. 1 dc in each st around. Join w sl st in 1st d . 35 dc

Round 15 :

Ch 2, * 1 dc in next 6 sts, 2 dc in next. Repeat from * around. Join w sl st in first dc. 40 dc

Round 16 :

Ch 2, 1 dc in each st around. Join w sl st in 1st dc. 40 dc

Round 17 :

Ch2, *1dc in next 4 st, 2 dc in next. Repeat from * around. Join w sl st in 1st dc. 48 dc

Round 18 :

Ch 2, 1 dc in each st around. Join w sl st in 1st dc. 48 dc

Round 19 :

Ch 2, *1dc in next 5 sts, 2 dc in next. Repeat from * around. Join w sl st in 1st dc. 56 dc

Round 20 :

Ch 2, 1 dc in each st around. Join w sl st in 1st dc. 56 dc

Round 21 :

Ch 2, 1 dc in each st around. Join w sl st in 1st dc. 56 dc

Round 22 :

Ch 2, 1 dc in each st around. Join w sl st in 1st dc. 56 dc

Round 23 :

Ch 2, 1 dc in each st around. Join w sl st in 1st dc. 56 dc

Round 24 :

Ch 2, *1dc in next 12 sts, dc2tog. Repeat from * around. Join w sl st in 1st dc. 52 dc NOTE***To make a longer, larger fin to fit 3-6 months size, repeat rows #19-23, then continue to #24

Round 25 :

Ch2, *1dc in next 11 sts, dc2tog. Repeat from * around. Join w sl st in 1st dc. 48 dc

Round 26 :

Ch2, * 1dc in next 10 sts, dc2tog. Repeat from * around. Join w sl st in 1st dc. 44 dc

Round 27 :

Ch 2, 1dc in each st around. Join with sl st in 1st dc. 44 dc.

Round 28 :

28. SHELL scalloped edge trim on top: ch 3, DC in same st 4x, this creates first shell, **sk 1 st. sl st in the next ch, sk 1 stitch, DC in next st 5x. Continue around until you are back at the beginning. Fasten off; weave in ends on the inside of Tail. You should have a tail that looks like this & a close up of the scalloped edge :

Info :

**Make a STRING: With same color yarn, chain a long cord, enough to weave into the tail body at the top near the shells, to tighten and gather the outfit so it stays on the little one. It should be long enough to be able to tie like a shoe (more is better than less). Weave in the chain rope with your crochet hook, about every 2 stitches apart, creating the tie towards the back of the outfit, leave tails free.

— Fins :

Info :

FINS: Make 2. I like to use J or K hook, this creates a large flipper/fin look on the mermaid. You can adjust and use a smaller hook for a smaller fin.

Round 1 :

Ch 28

Round 2 :

1hdc in 2nd ch from hook and each remaining 29 ch. 27hdc

Round 3 :

Ch1 turn, 1 hdc in flo next 26 st, leave last stitch open 26 hdc

Round 4 :

Ch 1 turn, skip 1 st, hdc in flo next 25 sts. 25 hdc

Round 5 :

Ch1 turn, 1hdc in flo next 23 hdc leave last 2 sts open 23 hdc

Round 6 :

Ch 1 turn, skip 1st, 1 hdc in flo next 22 sts. 22hdc

Round 7 :

Ch1 turn, 1 hdc in flo next 21sts, leave last st open. 21 hdc

Round 8 :

Ch1 turn, skip 3 sts, 1 hdc in flo next 18 sts. 18hdc

Round 9 :

Ch1 turn, 1 hdc in flo next 14 sts, sl st next 2 sts. 16 sts

Round 10 :

Ch1 turn, skip 2 sl st. hdc next 14 sts. Fasten off. 14 hdc.

Round 11 :

SHELL: Create a shell stitch on the longest side of the fin (as you did above on the tail top. Start on the edge that is NOT angled. Skip 2 chains on the end before beginning join the yarn 2nd chain from end with a slip stitch. (you won't see this part when the fin is sewn onto the tail so there will be a tiny gap at these ends-don't worry). Start by Ch 3, DC4 x in same st, **sk 1 st. sl st in next ch, sk 1 stitch, DC in next st 5x. Continue to the end of the fin. You should have 4-5 shells. It doesn't matter how many you create, as long as each fin has the same amount so it doesn't look uneven when you sew it on the tail. This example has 5, sometimes I end up with 4. When you come to the end, the last shell will create a rounded edge, fasten off, and weave in ends on back side.

Info :

With a yarn needle and same color yarn, sew these two pieces together in the center to create a flipper. You could also slip stitch the 2 pieces together; either way will work just fine.

Info :

With yarn needle, and yarn, weave a piece of yarn through the top of your big flipper, you just created, leave two tail pieces of yarn at the ends. Pull the 2 ends so the top edging gathers, don't worry if it looks a little crooked or gets goofy looking, you can adjust later.

Info :

Pin this gathered flipper to the bottom of your tail that you just created. Make sure your seam area is on either side. Start along one side of the bottom point of the tail, I usually start at the point bottom and count up about 4-5 rows. You can gather and scrunch together and adjust as you go, pinning as you work your way around. Turn it over when your done to see what the front will look like.

Info :

Pin 4-5 rows up from bottom point and sew flippers on, adjust gathers as needed. When sewing keep seam area hidden on either side as you attach.

Info :

** Do not cut your strings that gather the flippers until you have completely sewn on the flippers. Start hand-sewing with yarn or thread & needle. Do this for the front and back. You can remove your pins once you start attaching the flippers.

— Scales :

Info :

Scales: Use H hook to make a wavy scale look like this at the top of your fin.

Info :

Using a contrasting yarn of your choice, Join at the seam (usually on the side), with a sl st in the 2nd row underneath of your scalloped edge area. Do not get too close to the top or it will not look right when you’re finished. You can always rip it out if you are not happy with where it's located. After joining, work very loosely, this creates a wavier look: *ch5, skip 1 st, sl st in next 2 sts. Repeat from * around and join w sl st into first sl st. Repeat until the end. You can make 2-3 rows, whatever you like. Fasten off, tuck ends inside, and finish off.

— Bikini Band for TOP :

Info :

Bikini Band for TOP: use H hook.

Round 1 :

Ch 66(you can chain more for larger sizes, follow this same pattern) If using different texture yarn, size hook, you can adjust as needed; you do not have to chain a total of 66. I base this on how big babies chest is or will be.

Round 2 :

1dc in 2nd ch from hook and in each remaining ch. 6 DC at the end of this row. DO NOT TURN, work on the other side by going around and continuing. This is what it should resemble:

Round 3 :

Join w sl st into 1st dc and fasten off. Sew 1-2 buttons to the end of the top to use as a closure. This makes the top adjustable for most any size. It will resemble this:

— Headband :

Info :

Headband: Use H Hook . If you need it larger, make more chains- totally versatile.

Round 1 :

Ch 56, DC in 2nd ch from hook * ch 1 and skip a st, dc in next st. Repeat from * to end. Fasten off. Sew button on end for closure. The pattern resemble this effect: (it won't be curved, I curved it for the picture)

— Starfish (Larger for Headband) :

Round 1 :

Magic circle

Round 2 :

Ch1, 10 sc in circle, tighten and join w sl st in 1s sc. 10sc

Round 3 :

*1sc in 1st st, 2 sc in next sc. Repeat from * around. Join w sl st in 1st sc. 15sc

Round 4 :

Ch 10, sc in 2nd ch from hook, 1 hdc in next 2 ch, dc in next 3 ch, TR in last 2 ch.

Round 5 :

From the start of the point, count to the left 3 chains, insert your hook into the 4th chain and join the first point. It should not be bulky, should be smoothly joined as in the 3rd picture.

Round 6 :

Repeat steps 4 & 5. When you go to join the remaining points, you join I the 3rd chain(count 2 open chains to the left, joining in the 3rd chain).

Round 7 :

Do not fasten off, but continue around the entire starfish with a slip stitch, creating a trimmed edge and this will also create a more stable starfish, not too floppy. The ends will still curl a little, but not too much.

Round 8 :

Starfish for headband-sew pearls into the center of the starfish, creating a flower type look; use about 9 pearls. Hand sew the starfish onto the headband. It will be somewhat floppy, which is ok. If you position it correctly, you should be able to sew most of the center on and continue sewing as much as you can to keep it stable on the headband.

Round 9 :

Starfish for bikini top: After creating (2), sew 1 pearl in the center of each starfish, hand sew each starfish onto the bikini band. The tinier the size, the closer together the starfish will go; keep in mind these are covering the nipple areas of the baby.

— Starfish (Smaller for Bikini Top) :

Round 1 :

Magic circle

Round 2 :

Ch1, 10 sc in circle, tighten and join w sl st in 1s sc. 10sc

Round 3 :

*1sc in 1st st, 2 sc in next sc. Repeat from * around. Join w sl st in 1st sc. 15sc

Round 4 :

Ch 7, sc in 2nd ch from hook, 1 hdc in next 2 ch, dc in next ch, trc in last 2 ch.

Round 5 :

Skip a st and sc in next 2 sts

Round 6 :

Repeat steps 4 & 5 four more times. Fasten off.

— Shell Cups :

Row 1 :

6 chainless sc. Ch 1, turn.

Row 2 :

6 sc across.

Row 3 :

We will be increasing to 11 in this round. This row will alternate DC, FPDC, DC, FPDC, DC, FPDC, DC, FPDC, DC, FPDC, DC. Start with a standing double crochet (or chain 3 to count as first DC). Then make a DC in the front post of previous sc row SAME SPACE. *DC in next st. DC front post in SAME STITCH.* Continue* to end. End with DC. This row can get tricky, and I apologize for not having any close ups of this part. Just play around with it, and as long as you have alternating DCs and FPDCs adding up to 11 it should work!

Row 4 :

Standing Double Crochet OR Ch 3, then BPDC, DC, BPDC, DC, BPDC, DC, BPDC, DC, BPDC, Dc. (11 st).

Row 5 :

Standing Double Crochet OR Ch 3, then FPDC, DC, FPDC, DC, FPDC, DC, FPDC, DC, FPDC, DC. (11 st). Fasten off. Weave in ends.

Info :

TIE AROUND NECK. Chain 45. Fasten off. Weave through top outer corners of shells. This part is not adjustable, so go ahead and weave in your ends.( Step A)

Info :

TIE AROUND UPPER WAIST: Chain 75. Fasten off. Weave through bottom two corners of each shell. Once your ends are weaved in, they should measure the same length on either side (similar to a regular bathing top). (Step B)

Info :

*NOTE: If you look closely at the shells, you might be wondering why yours look different than the ones pictured. This is because I played around with technique before changing the pattern to what it is now, and the photos reflect my OLD pattern. The way I see it....if yours looks like a shell, then you did it right!! :)

Assembly Instructions

  • Sew the two fin pieces together at the center to create one flipper; weave a length of yarn through the top of the joined flipper and pull to gather so the top edge forms a natural curve before attaching.
  • Pin the gathered flipper to the bottom of the tail starting at the bottom point and working up about 4-5 rows on each side, then hand-sew the flipper in place using matching yarn for a smooth seam.
  • Do not cut the gathering strings until the flippers are completely sewn on; hand-sew the front and back edges securely, then remove pins and weave in ends.
  • Sew starfish to the headband or bikini band by hand; for headband starfish use about 9 pearls sewn into the center for a flower look and stitch through as much of the center as possible to keep it stable.
  • Weave the tie cord through the top scalloped shells and pull to gather to fit the baby; tie and secure so the tail stays on during wear.

Important Notes

  • 💡Use pins to position flippers and gather the fabric before sewing to ensure symmetrical placement and even gathers.
  • 💡Weave in ends as you go to avoid a bulky finish and to keep the inside of the tail tidy where it rests against the baby.
  • 💡Work increases and decreases carefully and count stitches at the end of each round to ensure the tail shape remains accurate and even.
  • 💡Do not cut gathering strings on the flippers until the flippers are fully sewn to the tail, this allows adjusting and final shaping.

This baby mermaid costume pattern gives you everything you need to make a sweet, photo-ready outfit complete with tail, fins, shell top, headband and pretty starfish accents. Customize colors and trims to match your vision and create a memorable handmade piece for a newborn photoshoot or gift. Have fun stitching and styling your little mermaid! 🧜‍♀️🧶

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FAQs

What size will the finished piece be?

The pattern is written to fit approximately 0-3 months; using smaller weight yarn and different hooks can make a smaller newborn version or repeating certain rows can extend it to 3-6 months.

Can I use different yarn weights for this pattern?

Yes, you can use different yarn weights but the finished size will change; choose an appropriate hook and be prepared to adjust chain counts or repeat rows to achieve the desired fit.

Do I need prior crochet experience for this pattern?

This pattern is rated intermediate because it uses increases, decreases, front and back post stitches, shells and joining techniques; basic familiarity with DC, HDC and slip stitch is helpful.

How long does this project typically take to complete?

Most crocheters finish the complete costume including tail, fins, top and headband in about 5-7 hours, depending on experience and any custom adjustments.

How should I attach the flippers to the tail?

Pin the gathered flipper to the bottom of the tail starting at the bottom point and work up 4-5 rows on each side, stitching carefully with a yarn needle and leaving gathering strings until fully sewn.