Handmade Halloween: A DIY Fish Costume That Won’t Flop | Free Pattern

JUL 13, 2018 updated May 20, 2021

There’s nothing fishy about making your kid’s Halloween costume, especially when it incorporates all of your favorite DIY elements like hot glue, felt, foam and of course, custom fabric! Sara Walk of Tell Love and Party is swimming over to the blog to share a costume that will shine amongst a sea of classroom costumes. Taking center stage for this friendly fish is our go-to fabric for costumes, Satin. Level-up your handmade Halloween game with Sara’s step-by-step tutorial and get a head start with our free PDF fish costume pattern. 

Aqua Mermaid Tail by katebillingsley | Teal Swiss Dot by binge_crafter

Sara: It’s time to start thinking about Halloween!  If you’re anything like me, and you prefer cute over scary…this fish costume is for you. It’s the cutest costume alive and perfect for all those sea loving kiddos out there. It’s simple to make, no advanced sewing skills needed. So let’s dive right in, shall we? Ha!


  • Body fabric: 1-2 yards* of Aqua Mermaid Tail by katebillingsley in Satin 
  • Head and fin fabric: 1 yard of Teal Swiss Dot by binge_crafter in Satin 
  • Free downloadable Fish Costume pattern (optional)
    • 3T – Finished fish is approximately 30″ wide
    • 4-5Y – Finished fish is approximately 34″ wide
  • 2 yards of Batting
  • Craft Foam – you can find this at your local craft store 
  • 8″ swatch of white felt
  • 8″ swatch of black felt
  • 1 yard of ribbon for your straps
  • Hot Glue
  • Scissors
  • Sewing Machine
  • Poster board
  • Fabric Pen

*Amount of fabric required is dependent on your child’s size. This costume was made for my five year old son who has the following measurements:

Height: 40″
Hips: 23″
Waist: 21″

Create the Fish Pattern 

1. Print out your free fish costume pattern and assemble. If you prefer a different look for your fish, use the poster board to design your own fish pattern. You can make any shape you would like but I stuck to a more bubbly rounded fish.

2. If you’ve drawn your own fish pattern, cut it into separate parts so you have the following: head, body, tail and fin. These will be your pattern pieces for the fish. I added a tiny piece of poster board at the opening of the tail so it had a part to attach to the body later.

Cut Out Your Fabric

3. Fold your fabric so the right sides face out.  Using your fabric pen, trace around the head and cut out. You should now have two fish head pieces in your head/fin fabric.

4. Cut out two more head pieces with your batting. Take your two satin head pieces and face them right sides together. Place a layer of batting on the top and bottom so your head pieces are layered in the following way: 

  1. Batting
  2. Satin
  3. Satin
  4. Batting

5. Pin around the head, leaving the longest edge unpinned, and stitch together with a 1/2″ seam allowance. Be sure to leave the longest edge open because you will need it open to insert the foam.

6. Repeat so you have two stitched head pieces.

7. Next, it’s time to make the fin. Repeat steps 3-5: Trace the fin, cut the fabric, cut the batting.

8. Pin around the fin, excluding the large opening. This is the part you will attach to the fish. Be sure to leave room so you can turn it right side out. Sew around the pinned area.

9. Repeat so you have two fin pieces. 

10. Repeat steps 3-4 with your tail pattern.

11. Pin and sew the tail pieces and batting, leaving an opening at the bottom of the tail so you can turn it right side out. 

12. Next, fold your fabric in half and cut out two body pieces using the fish body fabric. This fabric is my favorite! Make sure you figure out which way you want your scales facing before you cut. Cut out two batting pieces as well using your fish body pattern.

13. Take all your pieces for one side of the fish (1 head, 1 body, 1 ) and lay them out so you know where you want the placement of the fin and face.  

14. Pin the face of the fish to the body.  Make sure to pin through both sides with the batting facing out. Stitch in place, making sure to only sew the front layer and front lining together and then repeat with the fish back and lining. This will ensure your fish is one piece.

15. Pin on the fin and sew the entire body making sure to leave an opening so you can insert the foam. Flip the body right side out.

Pro tip: Make sure to stitch around the fin, not across, to attach to the body. Stitching across will result in the fin getting stuck on the inside of your fish body!

16. Cut out a foam sheet so it’s the same size or slightly smaller than the fish.  This does not need to look perfect, you just want it to fit nicely inside the fish.

17. Roll the foam and insert it into the opening. Once inserted, open up the foam and fit it into the fish.

18. Take your glue gun and glue the opening shut or hand stitch closed.

19. Repeat the above steps create the second fish body.

20. Cut out a tail fin from the foam and insert into the fin.

Pro tip: Cutting the foam in half makes it easier to insert into your fabric!

21. Now it’s time to attach the tail using your trusty glue gun. Glue the tail between the two openings in the back of the fish. Glue around the tail as well so that the whole back part of the fish is glued.

Make the Fish Eyes

22. Take your white and black felt and cut out four white eyes and two black pupils. Glue two white eyes together and then attach a black pupil in the center. 

Handmade Halloween: A DIY Fish Costume That Won't Flop | Spoonflower Blog

23. Glue the eyes onto the fish and glue the two heads together. Stop glueing before you reach the fish body fabric.

24. You should now you only have one opening – the middle of the fish.  This is where your child will get in and out of their costume.

Attach the Straps

25. Measure the length of the straps by having your child put on the costume and see where the straps should lay so the costume fits comfortably. Cut the ribbon based on this length and pin into place. 

Handmade Halloween: A DIY Fish Costume That Won't Flop | Spoonflower Blog

26. Glue or hand stitch the straps into place.

Handmade Halloween: A DIY Fish Costume That Won't Flop | Spoonflower Blog

Your fish is now finished and ready for some Halloween fun!  Looks swimmingly!

Handmade Halloween: A DIY Fish Costume That Won't Flop | Spoonflower Blog

Are you ready to dive into your next DIY project? Search the sea of fish inspired designs in the Marketplace to create an entire school of fish costumes for your family. 

About the Guest Blogger

Sara is the founder and creator at Tell Love and Party, a colorful party, DIY and lifestyle blog. From costumes to cake toppers, Sara uses her blog to showcase her latest creations. She is a world traveler, party enthusiast, chocolate advocator and is that girl who gets excited about everything. She lives by the beach with her husband and 3 boys, has a degree in visual communications and has worked in store design, window displays and merchandising with TOMS, Billabong and other companies before starting her own blog.

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  • Just a little insight – not having any batting at home, I used fleece instead and used only one layer – it\\\’s working perfectly. Am thinking I might topstitch the face? Thoughts?
    This is an amazing pattern and certainly easy to put together! Thank YOU!

    • Hi Liz,

      What a great suggestion and we think topstitching the face could add a nice finished look to the project! We’d love to see a photo of your finished fish. Happy making! -Meredith

    • Hi Kathryn,
      You can find the templates under the Materials list as a sub-bullet under “Free downloadable Fish Costume pattern.” Just click on either 3T or 4-5Y to get the size you’d like. Hope you enjoy!
      Suz from Spoonflower