No Sew DIY Mermaid Costume for Girls

In: DIY, Toddler
no sew DIY mermaid costume for a girl

Each fall when the leaves on trees on our street began to make their annual transition from lush green to vivid golds, oranges, and reds, my sisters and I would inevitably begin dreaming up what we wanted to dress up as for Halloween.

We were lucky enough to have a very creative and talented mother who could make our dreams come to fruition, whether we wanted to dress up as Belle from Beauty and the Beast or a Christmas tree complete with lights and ornaments.  Our Halloween costumes were always beautiful and unique.

I would like to continue this tradition with Baby Girl, but unfortunately I don’t have the same seamstress talent as my mother.  Even though I would love to learn how to sew, I just haven’t taken the time necessary to learn.

This year, rather than giving up the tradition, I’ve found a way to make to make a unique Halloween costume for Baby Girl without so much as touching a needle and thread.  Here’s my solution: a no sew DIY mermaid costume.

DIY mermaid costume

This mermaid costume is really easy to make and anyone can do it with just a few simple tools.  Plus, it doesn’t take too much time to create.  So if you’re in a pinch and need a cute Halloween costume for a little girl… then read on sister (or brother for any of you DIYing dads)!

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A dozen or so small seashells – I used green limpet shells which were approximately .5”-1”.

2 medium size clam or scallop shells

6” wide rolls of tulle (I used two spools for Baby Girl’s costume – one blue/one green), but the amount will vary depending on the age/size of the girl)

A tank top in the child’s size – I bought a pink American Apparel tank top on Amazon

1 yard of foldover elastic

Swarovski crystals – I used a pack of AB crystals in three sizes

1 yard of 1” ribbon – I used blue satin

Scissors – the sharper the better

Measuring tape

Hot glue gun and 1 glue stick

E-6000 glue





  1. First, measure the length from your child’s waist to the floor to determine the length of the mermaid skirt. Then measure around their waist to determine the length of the elastic for the mermaid skirt.  For instance, Baby Girl’s measurements were 16” waist to floor and 18” waist.

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  1. Once you have the waist measurement, add 5” to that amount and cut that length of elastic. Baby Girl’s waist was 18” so I cut a 23” piece of elastic.

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  1. Next double the measurement from waist to floor (16” becomes 32”) and then add 3” more to that number (for Baby Girl this brought me to 35”). Use this length to measure and cut pieces of tulle for the mermaid skirt.  I would start by cutting pieces from two entire spools of the 6” tulle, then cut more as needed.
  1. Temporarily tie the ends of the elastic you will use for the skirt to legs of a chair or other sturdy object where the elastic can be stretched out. I used the legs of a clothes rack.

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  1. Next you’ll tie the pieces of tulle to the elastic. First, take one piece of tulle and fold in half.  Then take the top folded part of the tulle and place it under the elastic.  Create a space in the top fold so you can bring the ends of the tulle up over the elastic and through the top folded part which now should look like a loop.  Pull on the ends of the tulle to tighten the knot.

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  1. Repeat the previous step with the remaining pieces of tulle until there is enough tulle on the elastic to wrap around the child’s waist, for Baby Girl it was 18”. As you are tying the knots make sure to slide the knots together so you can’t see the elastic in between the knots.  If you are using more than one color of tulle be sure to alternate colors, for instance I alternated with two green and then two blue.  Once you have finished tying the tulle onto the elastic, untie the elastic from the chair.

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  1. Next you’ll need to cut small slits into each piece of tulle to insert the ribbon into. To do this take each piece of tulle and measure two thirds of the way down from the elastic, fold the piece of tulle in half vertically and make a small cut with the scissors at the two thirds mark.  For Baby Girl’s skirt I made the cut 10” from the elastic and her overall length of the skirt was 16”.

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  1. When you have finished cutting the slits, take the yard of 1” ribbon and tie one end to one of the used spools of tulle (this is to make sure you don’t pull the ribbon all the way through the slits). Then thread the other end through the slits in each piece of tulle.

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  1. Once you have finished threading the ribbon, tie the two ends of the elastic together in a double knot, and then tie the two end of the ribbon together in a bow. The ribbon should be tied tight enough to gather the tulle together to help create the shape of a mermaid’s tail.

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  1. After the skirt is complete, you’ll need to shape the bottom of the skirt with the scissors to resemble a mermaid’s tail fins. The best way to do this is work with the front of the skirt first and then shape the back using the elastic tie as the center of the back.  To shape cut a deep inverted V into the tulle on the front of the skirt stopping an inch or so below the ribbon.  Round off the ends of the V with the scissors so the cut isn’t too blunt.  Repeat with the back side of the skirt.

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  1. Then with the front of the skirt facing you, cut a wide shallow V shape into the right and left sides of the skirt with the ribbon being the point of the V.  Again, round off and shape the ends so they resemble the tail fins of a mermaid.  For me this required a lot of small cuts into the tulle to fine tune it and get it looking just right.

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  1. Now that the skirt is complete, let’s turn our attention to the top. Start by cutting a piece of tulle an inch longer than the width of the tank top.  Twist the center of the piece of tulle and use the hot glue gun to glue the piece of tulle to the front of the tank top at the height of the chest (usually just under the arm holes of the tank top) making sure the twist is centered horizontally.
  1. Once the tulle is glued in place, use the hot glue gun again to glue the two larger scallop or clam shells on top of the tulle. Place one shell on either side of the twist approximately an inch or two away from the twist/center, making sure to place the smaller side of the shells on the inside.

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  1. Next use the hot glue gun to glue a limpet shell to the center of the twist with the underside (colorful side) of the shell facing up. Also, use the glue gun to glue limpet shells around the neckline equally spaced 1-2” apart, again with the underside facing up.

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  1. Last but not least you’ll need to use the E-6000 glue to glue on the Swarovski crystals. I used the medium sized crystals for inside the limpet shells and the largest crystals for around the neckline.  To glue the crystals pick up the crystal with the tweezers and use the toothpick to place a tiny dot of glue on the back of the crystal.  Then use the tweezers to place the crystal in its place.  See the image for placement of the crystals.  Make sure to give the glue 24 hours to fully dry.

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And there you have it… one easy, no sew, DIY mermaid costume for the little girl in your life!  Hope everyone has a very Happy Halloween!

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*I threw together this quick headband using leftover materials, knowing full well Baby Girl probably wouldn’t wear it and sure enough she ripped it right off!  Oh well, but here’s a photo in case you want to add this to your costume.

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