hwtm icons row

Easy Rainbow Unicorn Birthday Cake

Quick Jump To » Comments

PIN this unicorn cake recipe to try it later!

This fun & whimsical unicorn birthday cake has the magic going on inside AND out! 😉

The main rainbow part happens inside… and simple white frosting highlights these colorful layers. I also like how the cake is reminiscent of a big puffy cloud on the outside, with printable paper clouds “floating” above.

Unicorn Cake Topper

Note: The printable cake topper linked in the materials list is designed for a 1st birthday. Do you need a different age? Post a comment below and let me know. I’ll get it to you! :)



You’ll need:

  • 2 boxes of white cake mix
  • 4 tubs of white frosting
  • food coloring
  • marshmallows from Lucky Charms cereal
  • 8″ round cake pans
  • 8″ cardboard cake circle (optional)
  • frosting spatula
  • For the cake topper: white cardstock, scissors, clear straws, hot glue gun


1. Prepare the cake mix as directed on the box. Divide the cake batter evenly amongst 4 bowls, then tint each bowl of batter a different color. (Note: If you only have 2 cake pans, split this step in half and do it twice. So you’d prepare just one box – and 2 colors – at a time.)

2. Bake in 8” round cake pans. (1 color per pan)

3. After the cakes have completely cooled, use a long serrated knife to level them off slightly at the top so that they stack evenly. Use generous amounts of white frosting between the layers when stacking.

4. Add a “crumb coat” to the outside of the cake, which is a thin and messy-looking bottom frosting layer. Refrigerate the crumb coat for an hour.

5. Add another layer of frosting to the cake. This layer should go on nice and smooth over the crumb coat. Be extra generous with the frosting on the top of the cake, and use the back of your spatula or a spoon to create peaks for a “fluffy cloudy” look.

6. Decorate the cake with star sprinkles on top and candy marshmallows on the side. These heart and rainbow marshmallows were pulled from a box of breakfast cereal!

7. For the finishing touch, cut out my Unicorn Birthday Cake Topper and hot glue the clouds and unicorn to clear straws, then insert them into the cake! (You can also use bamboo skewers or party straws, but clear straws will give more of a “floating” look.)

For lots more ideas like this one, check out my original post: Simple & Sweet Unicorn Birthday Party Ideas.

PIN this unicorn cake recipe to try it later!

Magical Unicorn Printable Collection

Planning an unicorn party? Check out my Magical Unicorn printables. They make it so EASY to add pro designer style & personalization to your event. It’s like instant branding for your party! 🙌 Click here to shop now.


  1. Anna Akuretiya February 3, 2022 at 8:23 am

    Hi! Could you share a unicorn topper for a 5th birthday? Thanks!

Comments are closed.

Browse Party Ideas: