How to make a simple DIY mermaid cake

How To Make A Mermaid Cake The Simple Way

We recently celebrated the 4th birthday of our youngest daughter. Every year when you ask her what he wants for her birthday, her answer is always the same – CAKE! So each year I pretend I know what I’m doing and attempt to create a masterpiece she loves. This year that was a DIY mermaid cake theme.

How to make a simple DIY mermaid cake
This article may contain compensated links. See full disclosure here.

She’s a typical little girl in her love for unicorns, mermaids and pretty things so it didn’t take her long to put in her birthday theme request for the year.

While her birthday itself was a fairly low key event with extended family and a few friends, the cake was still super important in making her day special. So I wanted to share with you all how this really simple mermaid cake tutorial came together!


This DIY mermaid cake tutorial is really easy with step by step instructions for how I created my daughter’s 4th birthday cake. It didn’t take a lot of time to put together either, making it great if you are short on time yourself. It doesn’t need a great deal of prep either.

You can leave the mermaid tail cake topper out if you just want to go for an ocean theme cake instead. Or substitute it for a pre-made cake topper if you don’t want to DIY!

DIY Mermaid cake topper

If you make your seashell chocolates and mermaid cake decorations while your cakes are baking and cooling, they will be ready to use as soon as you’re able to decorate the cake too. This means the whole cake will take under 2 hours!

Or add an extra hour if you only have one round cake pan, as you will need to bake your cake layers separately. I had to do this.


Watch the quick tutorial video for making a mermaid theme birthday cake. Full step by step instructions below:

What you will need

How To Make A Mermaid Cake Instructions

  1. Preheat oven to recommended temperature as per your cake mix or if you are using a cake mix recipe, follow the directions.
  2. Bake 2 circular cakes using a 20cm cake pan like this one. Allow cakes to completely cool before decorating.
  3. While your cakes are baking, melt around 100 grams of chocolate in a heatproof bowl. I usually do this in the microwave for around 30-40 seconds, stir then repeat until melted.
  4. Add a couple of drop of food colouring to your melted chocolate to achieve the desired colour. I did this in batches using different colours. Once mixed, pour into your chocolate moulds. Place in refrigerator to set.
    Edible slime birthday cake
  5. Mix up buttercream icing (or use the icing mix that comes with your cake mix if using one) using your electric mixer.
  6. Add blue food colouring to your icing mixture until you achieve the desired colour for your ‘water’.
  7. Spread a layer of icing on top of your first cake, then place the second cake on top. You can add a 3rd cake layer if you wish for a taller cake.
    DIY birthday cake for girls
  8. Ice your stacked cake completely, covering the sides and top of your cake.
  9. Add swirls of edible slime in blue or green, or both, to the top and sides of your cake. This can be messy but imperfect swirls are fine.
    How to make a simple DIY mermaid cake
  10. To create your mermaid tail topper, draw a mermaid tail shape on the back of your gold cardboard. I did mine freehand but you can use a template if needed. Cut out your shape then attach to a paddle pop stick using tape. Ensure half the stick remains free at the bottom to stick into the cake.
    Handmade mermaid tail cake topper
  11. Position your mermaid tail were you want it on the cake then add seashell chocolate around the top and sides
  12. Use pearl cake decorating candy to finish the look by sprinkling them around the cake for simple DIY mermaid cake decorating.
How to make a simple mermaid cake tutorial

The best thing about turning 4 is that there isn’t a lot needed to make it an amazing event! We really only had a DIY mermaid cake and some seashells scattered around the table. Yet that was enough to have our littlest miss telling the world about her mermaid party!

It sure turned out a lot better than my attempt at a Poppy troll head made of cupcakes for her big sister the year before. But even that made the kids happy. It’s the little things really!

If you are planning a kids birthday celebration soon, check out these fun ideas for birthday party entertainment if you are wanting to do something a little different next celebration.

You may also love these unicorn Rice Krispie treats – the perfect girly party food!

Do your kids get excited about homemade birthday cakes too? Save this post to Pinterest via the image below! Be sure to follow me on Facebook or YouTube for more occasion ideas like this!

DIY Mermaid cake - ocean theme party for kids

Leave a Comment

Scroll to Top