What size will the finished piece be?

The pattern as written is sized approximately for a 0-3 month baby (tail about 14 inches long from top to bottom without fins). You can make adjustments by changing hook size or repeating shaping rows for larger sizes.

Can I use different yarn weights for this pattern?

Yes, different yarn weights will change the finished size. The pattern uses worsted weight (4/medium) yarn; using bulkier yarn with larger hooks will create a chunkier, larger costume while thinner yarn will create a smaller, more delicate set.

Do I need prior crochet experience for this pattern?

This pattern is rated intermediate and includes increases, decreases, front and back post stitches, and assembly steps, so basic crochet skills and experience with shaping rounds are recommended.

How long does this project typically take to complete?

Most crocheters complete the full costume in about 5-7 hours depending on experience, customization, and how many accessories you make.

Mermaid Costume Crochet Pattern

Switch Things Up

I love to change up the colors to create different moods: try ocean blues and greens for a classic mermaid, or pinks and purples for a playful look.

I often use a bulky yarn and larger hooks if I want a chunkier, cuddle-friendly version; conversely, a smaller hook and lighter yarn make an adorable mini tail.

I sometimes add a thin wire inside the flipper edges for a slightly posable fin; just be sure to wrap the wire and secure it so it cannot poke through.

I will often substitute beads or sequins on the scalloped shell edge for a bit of sparkle—just sew them on after finishing so they are secure.

If I want a different texture, I add a second contrasting color row of FPDC/BPDC around the top to make the scale area pop and look more dimensional.

I sometimes turn the starfish into tiny brooches by attaching a small safety pin on the back before sewing them to the band so they can be removed and repositioned.

Want a bigger size? I repeat the increase rounds in the tail a few more times and add extra rows between shaping rounds to lengthen and widen the tail.

For a newborn-safe version I use softer yarn like Simply Soft and a K hook to keep everything gentle and slightly stretchier; test fit often when adjusting sizing.

I also like to mix yarn weights for the scales row—one row in a fuzzy yarn creates a cloud-like effect that looks adorable in photos.

Finally, I use different closures for the bikini band: small buttons for adjustability, or a short velcro strip for quick on/off use when making outfits for little ones.

Mermaid Costume Crochet Pattern

Create a charming handmade mermaid costume complete with a textured tail, scalloped shell edge, flipper fins, a headband with starfish, and an optional bikini or shell top. This pattern walks you through each piece with clear step-by-step instructions and photos so you can make a perfect fit for a baby or small child. Customize colors and yarn weights to make a tiny treasure or a keepsake costume you will love to gift.

Intermediate 5-7 Hours

Materials Needed for Mermaid Costume Crochet Pattern

— Main Fabric

01
Worsted weight yarn (4WW/medium) - main color (Red Heart Super Saver or Love This Yarn recommended)
02
Accent yarn (contrasting color) for scales or trim - same weight as main yarn
03
Option: Simply Soft or similar softer worsted weight yarn for newborn-size tail (recommended with K hook)
04
Small amount of yarn for strings, pearls, or decorative stitching

— Tools Required

01
Crochet hooks: H (5.0 mm), I (5.5 mm), J (6.0 mm), K (6.5 mm) - use based on your yarn and desired sizing
02
Yarn needle (tapestry needle) for sewing and weaving in ends
03
Scissors
04
Measuring tape or ruler
05
Stitch markers
06
Pins for assembly
07
Buttons (1-2) for bikini top closure
08
Pearls or beads for starfish centers (optional)

Progress Tracker

0% Complete

— Tail :

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).

Round 3 :

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

Ch2, *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 :

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.

Info :

You should have a tail that looks like the photo in the pattern. Weave in ends on the inside of tail after scalloped edge is completed.

Item Name (P1) :

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 :

Round 1 :

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. Ch 28.

Round 2 :

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

Round 3 :

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

Round 4 :

Ch1 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. 22 hdc

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. 18 hdc

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 :

You will flip the fin on the right over to create the flipper look. 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 :

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. 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. 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 :

Round 1 :

use H hook. 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.

— Headband :

Round 1 :

Use H Hook. 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.

— Larger Starfish(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 shown in the pictures.

Round 6 :

Repeat steps 4 & 5. When you go to join the remaining points, you join 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.

— Smaller Starfish :

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 :

Round 1 :

MAKE 2 (these might take some practice, mine did not turn out like this at first. Try adjusting yarn thickness or using a smaller hook-keep practicing until you get the look you like). Row 1. 6 chainless sc. Ch 1, turn.

Round 2 :

Row 2. 6 sc across.

Round 3 :

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!

Round 4 :

Row 4. Standing Double Crochet OR Ch 3, then BPDC, DC, BPDC, DC, BPDC, DC, BPDC, Dc. (11 st).

Round 5 :

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.

Round 6 :

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)

Round 7 :

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)

Assembly Instructions

Pin the gathered flipper to the bottom of the tail starting at the bottom point and counting up about 4-5 rows on each side, then hand-sew securely with a yarn needle.
Sew the two fin pieces together at the center to create a flipper, then weave a piece of yarn through the top edge and pull to gather before pinning to the tail.
Weave the long string/chain into the top rows beneath the shell scalloped edge and pull to tighten so the tail stays on; leave tails long for tying.
Sew starfish onto the bikini band or headband, positioning pearls in the center of each starfish and hand-sewing to secure them in place.
Attach shell cups by weaving in the neck and waist ties through the shell corners, adjusting the fit and finishing by weaving in ends.
Pin pieces and adjust placement before final sewing; remove pins as you hand-sew pieces down to secure the final positions.

Important Notes

💡You will join each row by SL ST after each round at the top of your prior row beginning stitch; this creates a smooth even seam.
💡Do not cut the gathering strings for the flippers until you have completely sewn on the flippers; leave them until the piece is secure.
💡Weave in ends on the inside of the tail and fasten off securely after finishing scalloped or shell edges.
💡Pin and measure placement of flippers, shells, and starfish before sewing to ensure symmetry and correct spacing.

This mermaid costume pattern gives you everything you need to make a tiny, picture-perfect outfit with a textured tail, scalloped shell edge, flippers, headband, and optional bikini or shell top. Customize with your favorite colors and yarns to create a unique look that makes baby photos and dress-up extra special. Have fun stitching, gathering, and styling — and enjoy every magical finishing touch. 🧶🧜‍♀️

Mermaid Costume Crochet Pattern

Intermediate Level

Weekend Treat

Playful Twist

About This Mermaid Costume Crochet Pattern

Why You'll Love This Mermaid Costume Crochet Pattern

Switch Things Up

Common Mistakes & How to Fix Them

Mermaid Costume Crochet Pattern

Materials Needed for Mermaid Costume Crochet Pattern

— Main Fabric

— Tools Required

Progress Tracker

— Tail :

Round 1 :

Round 2 :

Round 3 :

Round 4 :

Round 5 :

Round 6 :

Round 7 :

Round 8 :

Round 9 :

Round 10 :

Round 11 :

Round 12 :

Round 13 :

Round 14 :

Round 15 :

Round 16 :

Round 17 :

Round 18 :

Round 19 :

Round 20 :

Round 21 :

Round 22 :

Round 23 :

Round 24 :

Round 25 :

Round 26 :

Round 27 :

Round 28 :

Info :

Item Name (P1) :

— Fins :

Round 1 :

Round 2 :

Round 3 :

Round 4 :

Round 5 :

Round 6 :

Round 7 :

Round 8 :

Round 9 :

Round 10 :

Round 11 :

Info :

Info :

Info :

Info :

— Scales :

Info :

— Bikini Band for TOP :

Round 1 :

Round 2 :

Round 3 :

— Headband :

Round 1 :

— Larger Starfish(Headband) :

Round 1 :

Round 2 :

Round 3 :

Round 4 :

Round 5 :

Round 6 :

Round 7 :

Round 8 :

Round 9 :

— Smaller Starfish :

Round 1 :

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