DIY Toddler Fish Halloween Costume

Last Halloween, Marin wanted to be a fish. This posed a bit of a problem since all the fish patterns I could find were ridiculous. The girl was not even two – how could she walk in this?

After consulting with Ali, I decided to go rogue when I found this picture online. There was no pattern to be found and no instructions on how to create a similar costume. Turns out that creating a cute little fish costume isn’t so hard! Here are my steps:

1. Get a base for the costume. Gap had a long sleeve shirt and leggings in aqua that would make a great base for the costume. I went with blue/green colors because I was afraid that going the goldfish route might look too much like a duck if you couldn’t see the fins. There are a lot of cute ducks out there at Halloween, but I didn’t want anyone thinking Marin was a duck if she wanted to be a fish!

2. Wait for a JoAnn sale and get some felt.  I also picked up some irridescent fabric for the fish belly, Peltex to make the fins sturdy, matching thread, velcro strips, a headband, and styrofoam balls (more on these later). I picked up about a yard of each fabric.

3. Get some measurements of the little one. Luckily I had just seen Marin a week or so earlier and was able to get some basic measurements to make sure nothing was too tight.

4. I started out by making a vest of felt. I could then sew the iridescent fabric to the front for the fish belly and the fins to the back for the scales. I used a pattern from her costume last year, which was a candy corn, for basic shape.

5. After cutting two pieces like this, I moved on to the fish belly, which needed to be a little bigger than the vest so I could wrap it around and sew a hem all the way around. I used the vest I had already cut as a pattern, then pinned the sides in.

6. Time to measure the fins. 4 inches seemed about right, but I used an index card for scale. Then I just cut the index card so it could be my pattern for the fins.

7. Now I used the fin pattern to cut all the fins. Note that its hard to see in the picture below, but I folded the felt and cut two layers. So the felt below is folded at the top to make two layers. This is so I can sew Peltex in between to make them sturdy. I cut a bunch of these and then laid them out to see when the back looked “full” of scales. Then I ironed the crease at the top of each scale.

8. Next I cut a layer of Peltex a little smaller than each scale (so it could slip inside without having white Peltex sticking out!) and sewed that into each scale. You could definitely get fusible Peltex and just iron it in.

9. Next I made a little tail fin. I needed The Huz’s help making the pattern. Again, I cut two layers of felt and a slightly smaller layer of Peltex for in between, and sewed the edges.

10. Now back to the vest. I uses iron-on Peltex for the inside of the vest to make sure it was sturdy and wouldn’t sag with the weight of the scales. I cut some Peltex a little smaller than the felt and ironed it right on to both the front and back of the vest.

11. Time to sew on the iridescent fish belly:

12. Now all the pieces are ready to be sewn together!

13. Line the scales up where you want them and sew a little seam at the top of each scale (the fold). Repeat until all the scales are on, then sew on the tail fin as well.

14. I wanted the costume to be easy on/off, so instead of sewing the shoulders and sides, I just sewed on velcro.

15. Now for her fishy eyes! As I said at the beginning, I picked up some styrofoam balls at JoAnn and cut them in half. These are super hard to cut. I had to enlist The Huz again.

16. Draw the eyes on with a sharpie, and hot glue them to your headband.

17. Then I had a last minute idea that Marin needed pectoral fins, so I cut some more felt and Peltex and sewed it right to her Gap long sleeve shirt.

18. Time to put all the pieces together – its done!

Here she is wearing it. Marin was just the cutest little fish I ever did see!



9 thoughts on “DIY Toddler Fish Halloween Costume

  1. melodee says:

    thank you for sharing this awesome idea! I am doing research for making a blowfish costume for a child to wear in her school play and this is really an awesome tutorial that I can see my way into changing up a bit to make into what we need! you are VERY creative!

  2. Rachel says:

    Hi Molly,

    This is simply adorable! Thanks for sharing such a great tutorial! I just linked to it from my holiday craft site:

    Please let me know if it’s okay to link to your projects like this in the future.


    • Molly says:

      Happy to help, Rachel! Of course you can link to any of my posts! Checking out your site now!

      • Rachel says:

        Hi Molly,

        Thanks so much! Would you mind sending me an email so I can ask you a couple questions? My email is rbernstein (at)


  3. Erin says:

    This is the only fish costume pattern/inspiration I have been able to find for my little man’s 2nd halloween costume. Thank you SO MUCH!! I love it and cannot wait to get started on it.

  4. […] belly sew     (hmmm… I guess they get my fish costume?) mouse poop in quinoa      (huh!?!?) ironic mattress      (huh?!?!) how many calories […]

  5. M says:

    Thank you for your idea. My daughter wants me to make a fish costume for my 2 year old grandson. I found your post. I liked your approach. Off to JoAnn’s for felt. And yes I have my coupons. And of course he’s in a different state. So I’ll be doing it based on measurements she sending.

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