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Mermaid Costume Crochet Pattern

Mermaid Costume Crochet Pattern
4.4★ Rating
8-10 Hours Time Needed
2.0K 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.

⏱️

All-Day Adventure

Requires 8-10 hours, ideal for a full day of immersive crocheting.

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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 complete baby mermaid costume including a tapered tail with scalloped edge, removable flipper-style fins, a headband, and two options for the bikini top: starfish or shell cups. The pattern explains shaping, scalloping, and an optional scale trim so you can customize the finish. Clear step-by-step numbered rounds and helpful photos make it straightforward to follow.

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

Designed for babies (0-3 months base size) but easy to adjust with different yarns and hook sizes for larger sizes. Includes finishing and assembly tips to secure flippers and decorate the headband or bikini with pearls or buttons.

Why You'll Love This Mermaid Costume Crochet Pattern

I absolutely love this pattern because it brings playful creativity to a practical project that you can customize. I enjoy how the scalloped edge and optional scales let you add small details that make each costume unique. The flipper assembly gives a satisfying shaping step where you can tune the look and fit. And sewing on the starfish or pearls is a lovely finishing touch that turns a simple project into something special I enjoy gifting.

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 customizing this pattern by changing yarn colors; you can create ombre tails or contrasting shells for a dramatic effect.

I often swap the main yarn for a bulky yarn and larger hook to make a chunky toddler-sized tail; adjust the fin rows accordingly.

I sometimes add sparkly or metallic accent yarn for the shell trim to give the costume a shimmery ocean look.

I recommend trying a smaller hook and softer baby yarn to create a newborn-sized tail that stays snug for photos.

Want a more structured fin? I add a small piece of flexible plastic or a doubled fabric interfacing inside the flipper when sewing to hold its shape.

I like placing the starfish closer together on the bikini band for tinier babies and wider apart for larger sizes to balance coverage and style.

For a more realistic scale effect, I crochet 2-3 rows of the scale motif in a slightly lighter color and block them gently to relax the stitches.

I sometimes embroider subtle wave lines on the tail with a contrasting thread to suggest texture and movement.

To personalize gifts, add a monogram on the inside of the tail top or a tiny tag sewn into the seam with a name or date.

If you prefer an easier closure, replace button fastenings with snaps or a small piece of elastic woven into the bikini band for stretch.

I also enjoy combining shell cups with a tiny crocheted ruffle edge instead of scallops for a different feminine look.

Finally, feel free to mix techniques: use the scalloped shell trim on the headband or make the starfish in larger sizes as a decorative collar piece.

Common Mistakes & How to Fix Them

✗ Skipping the slip stitch join at the end of rows can cause uneven seams and gaps; always join each round with a SL ST at the top of the beginning stitch as directed. ✗ Working with inconsistent tension makes the tail shape uneven and harder to fit; maintain even, moderate tension and check stitch counts frequently to stay consistent. ✗ Cutting the gathering strings on the flippers too early will lose your ability to adjust fit; keep strings intact until you have sewn both front and back flippers securely. ✗ Not counting stitches during increase/decrease rounds will distort shaping; count your stitches after each increase or decrease round and rip back if the count does not match the pattern. ✗ Using the wrong hook size for the yarn weight changes final size drastically; follow yarn and hook suggestions and make a small swatch to check gauge before starting.

Mermaid Costume Crochet Pattern

Make a charming handmade mermaid costume for a baby with this full crochet pattern. You get complete instructions for a tail, scalloped trim, matching fins, a headband, and a choice of starfish or shell bikini top. The pattern is photo-assisted and written so you can customize size and yarn for the look you want. Perfect for gifting, photo props, or imaginative play.

Intermediate 8-10 Hours

Materials Needed for Mermaid Costume Crochet Pattern

— Main Fabric

  • 01
    4WW (medium) weight yarn (4-weight) - main color for tail and fins (amount varies by size, approx 100-200g depending on size)
  • 02
    Red Heart Super Saver - example yarn used in pattern photos
  • 03
    Love This Yarn (similar weight to Red Heart) - suggested alternative
  • 04
    Simply Soft (lighter/softer yarn) - recommended for smaller newborn-sized fin/tail
  • 05
    Contrasting yarn for scale trim or accent rows (small amounts, about 10-30g)
  • 06
    Baby yarn (lighter weight) suggested if creating a newborn/smaller version

— Tools Required

  • 01
    Crochet hooks: H (5.0mm), I (5.5mm), J (6.0mm), K (6.5mm) depending on piece and desired size
  • 02
    Yarn needle for sewing and weaving in ends
  • 03
    Sewing needle and thread for attaching pearls or buttons
  • 04
    Buttons (1-2) for bikini band and headband closure
  • 05
    Scissors
  • 06
    Pins for pinning and assembling flippers
  • 07
    Measuring tape or ruler
  • 08
    Stitch markers (optional) to mark joins and beginning of rounds
  • 09
    Pearls or decorative 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 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 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 :

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, 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 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 :

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 :

1 hdc in 2nd ch from hook and each remaining 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, 1 hdc 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 reference). You will flip the fin on the right over to create this look.

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 :

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.

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 :

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.

Info :

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.

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. The pattern resemble this effect: (it won't be curved, I curved it for the picture)

— Larger Starfish (HEADBAND) :

Step 1 :

Magic circle

Step 2 :

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

Step 3 :

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

Step 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.

Step 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.

Step 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).

Step 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.

Step 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.

Step 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 :

Step 1 :

Magic circle

Step 2 :

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

Step 3 :

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

Step 4 :

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

Step 5 :

Skip a st and sc in next 2 sts

Step 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

  • Weave the string through the top of the tail near the scalloped shells, gather and tie so the tail stays on the baby; leave tails free for adjustment.
  • Sew two fin pieces together down the center using a yarn needle and same color yarn, then gather the top edge before pinning it to the tail.
  • Pin the gathered flipper to the bottom of the tail, starting at the point and working up about 4-5 rows; hand-sew front and back then remove pins and weave in ends.
  • Attach the bikini band by sewing 1-2 buttons to one end so it can be buttoned closed; sew starfish onto the band or headband using pearls for centers as decoration.

Important Notes

  • 💡Join each row by SL ST after each round at the top of your prior row beginning stitch to create an even seam.
  • 💡Do not cut the gathering strings on the flippers until you have completely sewn both the front and back pieces in place.
  • 💡Adjust hook size and yarn weight to change final sizing; smaller hooks create tighter fabric for smaller babies, larger hooks make the costume bigger.

This playful little mermaid costume is perfect for newborn photo shoots, baby showers, or a handmade gift to treasure. It includes a tapered tail with scallops, removable flippers, a headband, and options for starfish or shell bikini tops. Customize colors and trims to match your vision and enjoy every stitch! 🧶🧜‍♀️✨

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FAQs

What size will the finished piece be?

The pattern is written for approximately 0-3 months size for the tail; finished measurements will vary with yarn and hook, but the tail is about 14" from top to bottom before fins when made as shown.

Can I use different yarn weights for this pattern?

Yes, you can use different yarn weights but it will affect the finished size; choose an appropriate hook for your yarn and make a small swatch to estimate sizing.

Do I need prior crochet experience for this pattern?

This pattern is rated intermediate and uses stitches such as DC, FPDC, BPDC and shell trims; basic crochet experience and familiarity with post stitches is recommended.

How should I attach the flippers securely to the tail?

Pin the gathered flipper to the bottom of the tail, then hand-sew the front and back edges with yarn and needle. Keep gathering strings intact until sewing is complete to allow shaping adjustments.