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Mermaid Costume Crochet Pattern

Mermaid Costume Crochet Pattern
3.9★ Rating
5-7 Hours Time Needed
2.3K 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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Playful Twist

Fun patterns meet timeless design in pieces that express personality while remaining wonderfully wearable.

About This Mermaid Costume Crochet Pattern

This pattern creates a full mermaid costume for babies including a tail with scalloped top edge, removable flippers, a large flipper/fin assembly, headband and your choice of bikini starfish or shell top. The design includes instructions for scalloped trims, decorative scales and detailed finishing. Techniques include double crochet shaping, front loop work, post stitches and simple seaming for assembly.

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

The pattern is written for a 0-3 month size but gives notes to scale up or down by changing yarn weight and hook size. Plenty of photo examples and construction notes help you place fins and embellishments accurately.

Why You'll Love This Mermaid Costume Crochet Pattern

I absolutely love this pattern because it combines simple shaping with decorative stitches to create a magical finished piece. I enjoy how the scalloped shell edge and add-on fins let you customize the look for photos or gifts. I also love that the pattern is flexible — you can change yarn weight and hook size to make a tiny newborn tail or a slightly larger costume. Sewing the flippers on and adding starfish or shells is a rewarding finishing touch that makes the costume feel polished and handmade.

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

Switch Things Up

I love how easy it is to customize this pattern by switching yarn weights and hook sizes; try bulky yarn with a K or L hook to create a chunky, photo-friendly tail.

If you want a tiny keychain-sized version, use fingering weight yarn and a small hook and adjust the chain counts proportionally.

I often swap the scalloped shell color for a metallic or sparkly accent to give the tail a more magical, mermaid-like shimmer.

For a more realistic scale look, add multiple rows of the scale stitch in contrasting colors and alternate placement for an ombre effect.

Make the bikini top from a different textured yarn and use small buttons or snaps for a secure, adjustable closure.

I also like to embroider or needle-felt small details onto the fins for texture and personality, such as small bubbles or star shapes.

Consider adding a wire core inside the flipper seam if you want a more posable or structured fin that keeps a flared shape.

Use felt-backed pearls or safety embellishments for babies who will be wearing the costume for short photo sessions to minimize loose pieces.

Mix and match shell cups, starfish and scallops to create seasonal versions (pastels for spring, deep teals for ocean themed shoots).

For older children, simply chain more at the base and add extra rows to the tail body to scale up the project while keeping the same stitch patterns.

Common Mistakes & How to Fix Them

✗ Using the wrong hook size can drastically change the finished sizing; check the suggested hooks and adjust yarn weight or hook size to match the 0-3 month proportions before continuing. ✗ Skipping the slip stitch joins after each round will cause uneven edges and mismatched rows; always join each round with a sl st at the top of the beginning chain as directed. ✗ Working too tightly in the front loop only rows will make the tail stiff and harder to gather; maintain an even, slightly loose tension in FLO rows for a flexible fabric. ✗ Cutting gathering strings on the flippers before they are fully sewn on can undo your shaping; leave the strings in place until the flippers are completely hand-sewn and secured.

Mermaid Costume Crochet Pattern

Make a sweet handmade mermaid costume complete with a crocheted tail, flippers, scalloped edge trim, fins, headband and a choice of starfish bikini or shell top. This pattern is adjustable so you can size it for newborns up to a few months using different yarns and hook sizes. Clear step-by-step instructions with photos guide you through shaping, scalloped edges, decorative scales and assembly. Perfect for gifts, photoshoots, or imaginative play.

Intermediate 5-7 Hours

Materials Needed for Mermaid Costume Crochet Pattern

— Main Fabric

  • 01
    Medium weight yarn (4/Worsted/4WW) - recommended Red Heart Super Saver or 'Love This Yarn' as main tail yarn, amount varies by size (for 0-3 months sample sample tail used approximately one skein to two skeins depending on color and length)
  • 02
    Simply Soft or similar (same weight) can be used for a softer, slightly more drapey finish; use same weight yarn for consistent gauge
  • 03
    Contrasting accent yarn for scales or scalloped trim - small amounts (20-50g) in an accent color
  • 04
    Yarn for starfish and shell cups - small amounts (10-30g) per starfish/shell cup

— Tools Required

  • 01
    Crochet hook size I (5.5mm) and K (6.5mm) depending on yarn weight and desired sizing
  • 02
    Crochet hook size H (5.0mm) for scalloped edges, bikini band and headband
  • 03
    Crochet hook size J (6.0mm) optional for larger fins
  • 04
    Yarn needle for sewing and weaving in ends
  • 05
    Scissors
  • 06
    Measuring tape or ruler
  • 07
    Stitch markers or pins for holding flippers and seams
  • 08
    Pearls or small beads (about 9 per large starfish) and buttons (1-2) for closures
  • 09
    Pins for assembly and positioning flippers

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).

Info :

You should have something that looks like this: (photo reference in pattern)

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

Round 26 :

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

Round 27 :

Ch 2, 1 dc 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 this & a close up of the scalloped edge (photo references in pattern).

Infos :

**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 :

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 :

Your fins should look like this: (photo references). You will flip the fin on the right over to create this look and sew 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 a 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 :

Start pinning 4-5 rows up from bottom point. Close-up of pinned flippers. Backside of the tail with flipper pinned on. Sewing the flippers on the bottom (photo references).

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.

Info :

The front side will look like this once you flip it over: (photo reference)

— Scales :

Info :

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. 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 :

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.

— Headband :

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)

— 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 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.

— 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. MAKE 2 :

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!! :) Also the way the shells turn out will vary on how tight you crochet or the type of needle/yarn used, so don't panic if they don't look exactly like picture.

Assembly Instructions

  • Pin the gathered flipper to the bottom of the tail, starting at the point and pinning up about 4-5 rows on each side to position the seam evenly; hand-sew the flipper to the tail using a yarn needle and matching yarn.
  • Sew two fin pieces together at the center to create the large flipper; you can slip stitch or hand sew them together, then weave a piece of yarn through the top and pull the tail ends to gather the top edge before attaching to the tail.
  • Weave the chain string through the top scalloped edge of the tail at the shell row, spacing the cord about every two stitches so the tail can be tied and tightened to stay on the baby.
  • Attach starfish to bikini band or headband by hand-sewing pearls into the starfish center and securely sewing each starfish onto the band, spacing the bikini starfish to cover the chest area as directed.

Important Notes

  • 💡Join each round with a slip stitch at the top of your beginning chain to create a smooth, even seam.
  • 💡Work FLO rows and shell scallops with a slightly looser tension to maintain flexibility and a decorative edge.
  • 💡Do not cut the gathering strings on the flippers until the flippers are completely sewn on; leave the strings in place while sewing front and back.

This Mermaid Costume Pattern includes everything you need to make a darling baby mermaid tail, fins, scalloped trim, headband and starfish or shell bikini. It is easy to customize by changing yarn weight, hook size, and trim color to create a unique look. Perfect for photos, gifts, and imaginative play — enjoy crafting your little sea princess! 🧜‍♀️🧶

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FAQs

What size will the finished piece be?

The pattern is written for a 0-3 month size tail and fins when using medium weight yarn and the recommended hooks; sizing will change if you use thicker or thinner yarn.

Can I use different yarn weights for this pattern?

Yes, you can use different yarn weights, but this will affect final size and drape; adjust hook size accordingly and consider the proportion of tail to fins when scaling.

Do I need prior crochet experience for this pattern?

This pattern is rated intermediate, so basic knowledge of stitches like DC, HDC, working in rounds, and simple joining techniques is recommended for best results.

How long does this project typically take to complete?

Most crocheters complete the main tail and fins in 5-7 hours, plus additional time for sewing, scalloped edges, and embellishments; assembly and finishing may add extra time.