Family life Kids Sewing and Crafts

DIY Your Mermaid Costume!

Before lock down, I bought a 2m sequinned fabric from our local fabric store. Amelia was at a mum’s coffee group one Friday and fell in love with a mermaid costume that she wore ’till we had to leave. I thought to myself that I surely could make one similar!

More than 2 weeks have past and that piece of fabric have been a gateway to a whole load of imagination! We draped it over the seat of the couch to the floor and for a while, we pretended that it was a waterfall that her toy animals/ dolls came to swim/ drink at. Then it became a swimming hole/ shower water as we draped it over our heads with said toys. We made it into a wedding dress, a Sari, a ball dress, a blanket and more. Alas, this afternoon was probably the first afternoon since lock down that both girls had a full 2 hour afternoon nap, and it was bliss. I decided today was the day. With the motivation being a little sick of the piece of material (and pretending to swim underneath the fabric for the upteenth time), and my itching fingers waiting to get back to working on the sewing machine, I took the moment and went for it. I gained consent from Amelia prior her nap, so I was in the clear. Goodbye sequinned fabric, I won’t miss ya!

This project is a quick one and can be made without a sewing machine, albeit slower in process. It’s great for beginners or even something to do with your older kids, ages 4+. You can even whip this up for yourself for halloween or costume parties!

You will need:

  • Fabric material (length depending of the person you’re making it with, but 2m is plenty). Material that has no stretch/ one-way stretch at most. I used a sequinned one mentioned above, but the world is your oyster!
  • Butcher paper/ Kraft paper/ newspaper/ big piece of paper for your pattern
  • Pen
  • Scissors
  • Elastic (width optional) cut to your waist measurement and 2x on your bust measurement, minus 5-10cm on each (depending on your elastic and your measurements!)
  • Interfacing/ thin batting/ heavyweight material
  • Thread
  • Safety pin
  • Sewing machine/ hand-sewing needle


  • Measure: bust, length from your underarm to where you want the bodice to stop, waist, the length from waist to knee, the length of waist to your ankles

  • Plan: plan out your pattern. Transfer your measurement and plan onto your pattern paper. For this pattern, the waist line would be multiplied by 2 so that it can be gathered and stretched out freely with the elastic. I have also given 10cm at the bottom to attach the fish tail.
  • Create: In this pattern, I made it so that the fabric will be cut on fold. In this case, I would measure the length of the waist from the top (plus 1cm for seam allowance). Measure the length from your waist to your knee (plus the width of your elastic and add 1cm for seam allowance). Then measure the length from your waist to your ankles (plus 1cm seam allowance). After, measure 5cm (plus 1cm seam allowance) in. Connect a diagonal line from the end of the 5cm line and the waist-to-knee- length line. It should look like an upside down trapezium chopped in half. As for the tail, I free-hand this one from a 5cm line from the top and made one side of the tail straight-ish for the fold line, add 1cm seam allowance. Cut pattern to shape.
  • Cut: place and pin the pattern onto the material on fold. Cut material. Cut 1x on fold for the bodice, 2x on fold for the fish tail and 1x on fold for the fish tail on the interfacing fabric (I had some batting lying around the house, but any heavy-ish weight fabric/ interfacing would do the trick!)

  • Hem: hem the two diagonal sides. The fabric I use doesn’t really fray so I just folded it in, 1cm, once, but if your fabric frays then fold it in twice.
  • Join: sew the short sides together. I used French seam* on this one because it’s stronger and I suspect there will be a lot of tension with wearing it on and off all the time.
  • Fold: fold in the top of the bodice to the width of your elastic, plus 1cm. Pin and sew, but leave around 3-5cm gap for the elastic to go through

  • Elastic: attach a safety pin onto the end of the elastic. Thread through elastic into the gap that you just sewed. Gather material as you go (don’t worry about it being uneven because we can fix it after the elastic all goes through!). Be careful of the other end going through the hole, because you’ll be losing the other end in the gap! Once the elastic is all threaded through, pin and sew the elastics together and let it all go into the gap. Sew the gape of the gap to close the gap so the elastic can’t come out.

  • Fish tail: Put right sides together of the fish tail and have the interfacing piece on top of the fabric (fabric against fabric, with right sides together, then interfacing) and sew edges, leaving the top. Flip the fabric so that the right sides are exposed. Sew the top of the tail to the bottom of the bodice. On my one, the bottom of my bodice was a little longer than my tail, so I gathered the bottom of my bodice to make the length the same. I French seam this one too because I predict that either Amelia will step on it, or Phoebe will crawl up to the tail and pull it – either way, there’s going to be lots of tension!

  • Bodice: Cut 2x of fabric with the bust measurement across and the desired length plus the width of your elastic (plus 1cm allowance) x2. This is really important because the elastic is going on the top and bottom and if you don’t have this allowance, it might be shorter than you planned it! Sew sides together. Fold in the top and bottom to the width of your elastic, plus 1cm and pin. Sew the pinned folded bits, leaving 3-5cm opening. The rest is a repeat of step 8, but on the bodice!

Extra: I got a piece of extra material and used it to tie the middle of the bodice for another look. Totally optional!

It was lovely to have the opportunity to surprise Amelia when she woke up from her nap. She was hesitant to come to my call at first because she was “busy reading”, haha! But when she came and had a look, she was totally excited and couldn’t wait to get it on!

Would love to know if you made one for your daughter, cousins, sister, nieces, yourself or anyone else!

*French Seam: sew wrong sides together, 0.5cm. Trim edges so that between the seam and edge is less than 0.5cm. Fold the seam right sides together and sew 0.5cm. You will get the same finish on the right side, but on the wrong side of the fabric there will be no raw edges!

By Sarah

Sarah considers herself as a JAFA (just another friendly Aucklander) who loves Jesus. She is a wife of a bookworm-NBA-anime-loving husband, a mum of two very extroverted girls, and works as an RN. In her spare time (if she's not napping) she loves to meet with other women for a coffee or dessert, or you'll find her on the couch blobbing with a drink on one hand and a book/ phone on the other.

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