A Pirate & a DIY Mermaid Costume Tutorial

We’re getting really excited about Halloween around here. Last year, my husband and I chickened out and didn’t dress up with my daughter — mostly because any DIY costume I could throw together at the last minute would’ve looked crazy next to my daughter’s homemade peacock costume, which I made with care and forethought. But this year, I was determined for the whole family to dress up together. We went back and forth for a while about what we’d be, but we settled on seafaring people/creatures: My hubby and I will be pirates, the dog will be the pirate flag (yep!), and my daughter will be a beautiful, ethereal mermaid:

In our world, pirates and mermaids do battle, Pirates of the Caribbean style!

And the pirates (and our swords) always win! Lmao!

OK. Enough goofing around.

Because I knew making my daughter’s mermaid getup would require time and effort, I grabbed a store-bought costume for myself. I was really happy to see that Walmart had a great selection of women’s plus-sized Halloween costumes. In store, I found everything from a flapper, to a pirate to Disney’s Malificent in sizes up to 20. But online, the plus-sized selection is even better. Still, as much as I was excited about that, I had much more reason to be excited about something else: I didn’t NEED a plus-sized costume! (aff)

I actually got the Cutthroat Pirate costume marked Large (12-14), and it fit with room to spare! I suspect it runs big, because I’m in a size 16 for the moment (though not for long, if you’re following my weight loss journey). And if you say anything about the fact that you can’t see my eyes, you WILL feel the tip of my sword! (aff)

Lol! Seriously, I didn’t realize until after the fact that the hat was so low on my head.

And since I mentioned our Yorkie King will be the pirate flag, here’s the skull and bones dog sweater that he’ll be wearing (he wouldn’t sit still long enough for a pic wearing it) (aff):

Anyway, now here’s what you’ve all been waiting for: My daughter’s DIY mermaid costume and a tutorial so you can make one yourself!

DIY Mermaid Costume Tutorial

Like last year’s peacock costume, the idea I had was a bit bigger than my ability. I started with a sketch and figured it out from there:

It didn’t turn out exactly the same, but it gave me a starting point and a supply list. Here’s what you’ll need to recreate the look:

Mermaid Skirt

  • 1-2 yards of sequined fabric (I used 1.5 yards)
  • 1/2 yard each of blue & green organza
  • 1″ wide elastic
  • Rolls of blue & green tulle
  • Cardstock
  • Matching thread
  • Sewing machine
  • Hot glue gun


  • Blue long-sleeved leotard
  • Sequined trim
  • Heavy weight glitter canvas squares (found near the felt in a craft store or section) or felt
  • Rhinestones and other embellishments (shells, etc.)
  • Hot glue gun


  • Pattern from Genevieve Gail
  • Printer and cardstock
  • Heavy weight glitter canvas squares (found near the felt in a craft store or section) or felt
  • Rhinestones and other embellishments (shells, etc.)
  • Ribbon
  • Hot glue gun

Making the Mermaid Tail

1. Create a pattern

Lay your child (or yourself) down on a large piece of brown paper. Wrapping paper could work for this as well. Start about 3 inches above the waist and draw and outline of the waist, hips and legs to just before the ankles. Give yourself about 2″ of space between body and outline to account for the fact that this has to wrap around the body.  You can even do up to 4″ clearance. It is better to cut the fabric too big than too small. Have the child get up and freehand draw flippers at the bottom of the outline. Cut out the paper pattern.

2. Cut the sequined fabric

Fold your sequined fabric in half, right sides facing. Pin the paper pattern to the fabric, being sure to pin all the way around so the pattern won’t shift. Cut the fabric with about a 2″ seam allowance.

NOTE: You COULD line the skirt if you’d like, because the sequined fabric is a bit itchy. I didn’t line it, because I knew my daughter would be wearing leggings under the costume. If you plan to, now is the time to cut the lining.

3. Sew one side

Remove the pattern paper, but keep the two pieces of fabric pinned together. Next, sew along one side of the two facing pieces. Once done, you’ll have something that looks like this:

4. Make the waistband

Double fold the top of the skirt to create a waist band, and pin it. You are creating a pocket for the elastic waistband, so make sure your fold is at 1.5″ deep to accommodate the 1″ wide elastic. Finally, hem the waistband.

This is a good time to call your child over to wrap the skirt around them and make sure it will fit comfortably. Next, wrap a piece of elastic around your child’s waist to get an accurate waistband measurement. You want to stretch it a bit for the edges to touch, but not so much that it is tight or uncomfortable. Cut the elastic to the appropriate length.

Attach a safety pin to one end of the elastic to help you pass it through the waistband hem.

5. Finish the skirt

Fold the skirt together, right sides facing. At the waistband, make sure you can see the two ends of the elastic. Pin them together so they don’t bounce back into the hem. Then pin the open side of the skirt closed. Stitch it closed with a 1/2″ seam allowance. Double back over the elastic to make sure it is secure and be sure to backstitch your ends.

Be sure to leave the bottom of the skirt open!

6. Cut a split

Try the skirt on your child to test the fit. Depending on how much space you allowed in the pattern, you may not need to do this, but I wound up cutting a split up the back center of the skirt to make it easier for my daughter to walk. I didn’t hem the split at all, since this is the back of the costume. I simply cut a split from the bottom of the skirt to right above her knees.

7. Add the “scales”

At this point, the shape is right and it looks like a mermaid skirt. But I wanted a mermaid “tail”, so I added scales. But this part is tedious. Cut approximate half circles (more like half ovals) from your blue and green organza.  They don’t have to be perfect, so I cut them freehand. To speed up the process, I quadruple folded the fabric and stacked them on top of each other so I cut 4 green scales and 4 blue scales at the same time. You can cut them as big or small as you’d like, but the bigger the scales, the fewer you’ll have to add.

Starting from the bottom of the skirt on the left side, hot glue the top of each scale to the skirt using a thin bead of glue.

Slightly overlap the scale on the right with the one you just added. Then move up a row and overlap the scales like shingles. This doesn’t have to be perfect, so don’t worry about messing up or lining them up exactly. Alternate blue and green scales in each row.

I put scales on the front and back of the tail, but you can do just the front if you wish.

8. Finish the flippers

Remember that the bottom of the skirt is unhemmed. To cover this up, and also to help cover my daughter’s feet, I added tulle at the bottom of the skirt. However, the bottom needed a little structure first.

Put a piece of card stock under the bottom of the skirt and use a pencil to trace the outline of the tail shape. You’ll likely need a piece of cardstock for each side. Cut out the shape and hot glue it to the underside of the tail fin. Be sure to only glue it to the front of the skirt — NOT to the back! Let it dry for a bit.

Cut 8-10″ strips of blue and green tulle. Tie a blue strip to a green strip at the center to form a small bunch.

Hot glue these bunches to the bottom of the skirt, following the shape of the tailfin. You can trim any excess length once done. Do the same on the other side.

Again, its up to you whether you add tulle to the back of the skirt. I haven’t yet, but I plan to add it before Halloween just to give the back a little something extra.

The skirt is done! Step back and admire your handiwork, because this really the showpiece of the costume!

Making the Bodysuit

Start with a blue, long-sleeved bodysuit. You’ll need to create shells for the bodice. I freehand drew a shell shape on the back of some sequined canvas squares and cut them out.

For the rest of this, you’ll want your child to wear the leotard so you can place everything appropriately. Place the shell cutouts where you’d like them to go and safety pin them in place.

Also use safety pins to mark any other specific locations for embellishments. For example, I put safety pins just above where the waistband of the skirt would sit so I wouldn’t put any rhinestones too low. Rhinestones under an elastic waistband would get uncomfortable very quickly.

Have your child take off the leotard and hot glue the shell shapes in place. I also decided to glue some silver trim to the top edge of the shells because I liked it better than the scalloped edge I’d cut.

Finally, embellish the rest of the leotard however you’d like. I put sequined trim around the collar (only in front, so the back of the leotard would still stretch), as well as rhinestones on the bodice under the shells in arcs toward the waistband. I laid out the rhinestones before actually gluing them on, which is why the final layout differs from what’s shown below. I changed my mind about the vertical line of rhinestones down the middle that’s shown below and forgot to take a picture of the final layout. You can see it on the finished costume though.

You could attach real shells to the costume or add glitter, etc. This is your opportunity to get really creative.

Making the crown

I started with this pattern from Genevieve Gail. Print two copies of the pattern onto cardstock and cut it out. We’re simply using it as a shape reference. Trace the pattern on the back of your sequined canvas (or any other material you’d like to use to cover the crown). Cut out the shape and hot glue the canvas to the cardstock.

With the second pattern, cut out just the shell shape in the center. Cut each piece of the shell separately, rather than cutting it as one whole piece. Use this template to cut shell shapes from blue felt. Line up the shapes and glue them to the center of the crown.

Embellish the rest of the crown how you see fit. I used more rhinestones and a capiz shell I had kept that had broken off a piece of decor a long time ago. Again, you can use real shells, glue on some sand, use a starfish shape: Whatever you want! The more embellishments you layer on top of each other, the more elaborate the crown will appear.

Cut two pieces of ribbon about 14-20″ long. Cut slits at the two ends of the crown shape or use a powerful hole punch. Pass a piece of ribbon through the slit/hole and tie it off. You’ll use this ribbon to tie the crown around your child’s head.

You’re done!

The finishing touch to this costume was a blue wig we found at Walmart. Technically, it goes with a Monsters High costume, but my daughter loved the color and I knew it would be the perfect mermaid hair.

What do you think? I’m really, really happy with the way it turned out!

Looking for more DIY Halloween ideas?

Check out all the other homemade costumes I’ve created for my daughters over the years, along with other Halloween crafts:

Disclosure: I am a member of the Walmart Moms program. Walmart has provided me with compensation for sharing my store bought and DIY Halloween costumes with you. Participation is voluntary and as usual, all opinions are my own.

By jennae

Hi! I'm Jennae Petersen and I'm the eco diva who had the bright idea to share my journey toward green living with the blogosphere. Some of you may know me as the founder of Green Your Decor, my blog about eco-friendly home decor, as a Walmart Mom, from Twitter or from my organic cotton t-shirt line Differently Clothing. Stick around for a while!


    1. Thanks Cris! Not counting stuff I already had on hand (like thread, glue, etc.) or the wig, I’d say the total cost was about $30-35. Not bad, considering the retail price of a decent costume is right around the same, and this one is one of a kind 🙂

      For a teen/adult, I’d recommend buying at least 3 yards of the sequin fabric, but depending on the height of the person and her dress size, 4 yards might be safer. I hope that helps!

  1. Thanks so much for making this step-by-step. I’ve been tossing around my own ideas for our family Mermaid Halloween this year. Most costumes and patterns don’t have an actual tail, but just a frilly bottomed dress. Your costume is exactly what my daughter wants: a ‘real’ tail. 🙂 Can’t wait to get started on it!

  2. Wowza! I will have to read it again with a pattern in front of me, measuring tape next to me and pencil in hand. But this is ah-maz-ing!!! Someone just answered my biggest alterations questions!!!!!!!!!!!!!! I think I’ll hack up a couple of those 1.99 tees from Michaels and see what I can do with ’em!!!!
    You still and forever ROCK!!!!!!!!

  3. Wow, a beautiful mermaid skirt and you make this look so easy! (And I know it’s not!) – I have to make a mermaid tail for my daughter’s school play costume and I wasn’t sure what to do – your directions are great, so I’m going to give it a try as soon as I find some fabric. Thank you so much for sharing this!

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