Kid Mermaid Flutter Top Tutorial

This mermaid outfit that I made T for may be my favorite party get-up I’ve made one of the nieces so far. I just love it. When she told me she wanted to have a mermaid birthday party this mermaid flutter top and fin pants combo just popped into my head. I love how she can run and play but still be totally dressed up and girly in it. The best part is that it was relatively easy to make. Today I’m going to share my tutorial on how to make the top and I’ll have the pants tutorial up soon too.

How to make a child's mermaid costume from Rae Gun Ramblings

The fit is really loose and flexible but for T’s shirt (she’s 6) a yard of fabric and ribbon was more than enough. You need to make yourself a pattern. Don’t worry it’s not scary.

How to make a mermaid kids costume

Find yourself a shirt that more-or-less fits your kiddo. Fold it in half. Then trace the basic shape (you don’t need to trace sleeves if it has sleeves). Now you’ll want it to cut out a little so draw an angled line from the armpit. And you also want room to gather in the front and back so an an inch or two (depending on how much you want it to gather) to the center line). Now you have a pattern. Cut out FOUR of these. Then take two of them with right sides together and cut them shorter (I just eyeballed a curve). Now you should have two long pieces and two short pieces.

How to make a child's mermaid costume from Rae Gun Ramblings

  1. Now that you have your top pieces finish the bottom edges. I did this by serging a rolled edge along the bottom with my serger but you can finishing how ever you like folding under for a narrow hem or even a small zig zag on the sewing machine. Lay one top (shorter piece) on top of the bottom piece right side up then serge or zig zag sew along the top edge attaching both pieces. Do that to the remaining pieces.
  2. Next sew you want to sew the side seams. Put the top pieces right sides together (so you should have two short pieces touching and behind them the two long pieces) and sew down the sides. (not pictured)
  3. Finish the arm holes. I did this by serging the curve and then rolling under twice. You can just roll under twice though. Then sew down.
  4. Make the casing for the ribbon. Fold the top edge under a little wider than the width of your ribbon. Sew across. Repeat on the back.
  5. Take two pieces of ribbon and thread through the casing.
  6. Scrunch the top to be the width desired across the across and then sew down on the sides tacking the ribbon in place. You don’t have to sew down the ribbon but I like to since it controls how the top will lay.
  7. Tie the ribbon and you are good to go with a cute kid mermaid flutter top. (not pictured)

How to make a child's mermaid costume from Rae Gun Ramblings

If you haven’t had a chance to check out the mermaid party pictures you might want to do that I show you how to make super cute oyster looking cookies. And be sure to check back in next week for a full tutorial on how to make the mermaid pants complete with fun little fins.  And yes little sister L forced her way into the photo shoot as little sisters will do so she’s got the top photo :)


  1. This top is so cute! I want to make one for me! :)

  2. Adorable and perfect for summer!

  3. What a CUTE outfit. I’m wishing I had a little girl to throw a mermaid party for. Perhaps one day. Pinning :)

  4. The posed pictures of T are so adorable and really make her look like a mermaid!

  5. This is so cute! Found your blog on the aloha blog hop :)

  6. How cute is that!? What a fun costume! Thanks for sharing it at Monday Funday!

  7. Really pretty! The top turned out beautifully–looking forward to the mermaid pants!

    Planting Daffodils

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