How to Make a Stunning Rainbow Frosting Swirl (Unicorn Cupcakes)

Rainbow frosting is the literal frosting on the cake of your kid’s magical unicorn party. This swirl of primary colors evokes a sense of magic and excitement.

Also known as unicorn frosting, a well-executed rainbow frosting swirl sure has the WOW factor. It’s an easy way to add pops of color to your cake table, and it looks amazing in photos (and on social media).

And no one has to know how truly easy it is!

And let’s not forget the simple pleasure kids get from the rainbow color palette. From an early age, kids see something like a rainbow swirl and associate it with fun and cheerfulness. Just what you need for birthday cakes!

DIY Rainbow Swirl Frosting (Unicorn Cupcakes) - Press Print Party!

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I used this multicolored rainbow frosting on my super adorable unicorn cupcake cake for my magical unicorn party. I’ll be sharing all of the info for the rainbow frosting cupcakes along with the instructions for the frosting.


Rainbow Buttercream Ingredients

When it comes to decorating a cake, I enjoy making my own frosting first thing. For rainbow frosting, my favorite recipe is the Swiss meringue buttercream.

I’ll walk you through how to make that in this blog post but if you want the recipe card, you can find it on my buttercream post.

free printable coloring pages unicorn - Press Print Party!

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How to Make Swiss Meringue Buttercream

It is possible to use store-bought frosting for your rainbow unicorn cake, but you’ll be missing out on one of my favorite frostings if you don’t use my frosting recipe. In the steps for making frosting from scratch, I included my own tips for getting the best results. 

I do recommend using something like a Kitchen Aid mixer or hand mixer. I used the former. If you intend to use your frosting for filling or making multiple cake layers, you can add flavoring to your frosting at the end. 

Go here for the recipe card and full instructions with pictures.

  1. Choose a metal mixing bowl and saucepan. Make sure the bowl will fit in the top of the pan so you can make your “bain-marie.” 
  2. Add water to your pan and bring it to a simmer.  
  3. Place the mixing bowl on top of the pan. 
  4. Mix the egg whites and sugar in your mixing bowl. Stir constantly until the sugar is dissolved. You can now remove your mixing bowl from the pan. 
  5. Whisk the mixture until it becomes stiff. Once it stiffens, continue whisking for 6 more minutes on high.
  6. Switch to the paddle attachment. Add the butter in batches while beating on low or medium speed making sure each batch is well blended.
  7. Add the vanilla extract and beat on medium-high for 3-5 minutes until smooth. Beat on low for another 2 minutes to remove any air bubbles
Cupcake frosted with white Swiss meringue buttercream frosting - Press Print Party!

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5 images showing the progression on how to make Rainbow Swirl Frosting for Unicorn CupcakesHow to Prepare Your Rainbow Frosting

Now that you have prepared your buttercream frosting, let’s talk about adding color. To begin, pull out four bowls so you can use a different bowl for each color.

  1. Divide some of the white frosting into 4 separate bowls and color them with the food coloring. I chose pink, purple, yellow, and blue to match my party printables theme.
  2. Stir each buttercream, adding food coloring until the desired shade is achieved. You’ll want a vibrant color for rainbow cupcakes.
  3. Prepare a piping bag for each of the colors.
  4. Lay a piece of plastic wrap on a board.
  5. Pipe about 4-5 inches of each color next to each other (lay the pink and purple next to each other).
  6. Roll the saran wrap around all 4 colors (make sure not to put the saran wrap in between the colors).
  7. Twist both sides like a candy wrap.
  8. Prepare a whole bunch of these little bundles at once so you don’t have to stop in the middle of pipping to make more.
  9. Snip one of the ends and insert the cut end into another large piping bag ready with a piping tip.
  10. Now swirl the frosting on top of the cupcake or cake!!

Voila! Perfect unicorn frosting!

Here’s a quick video in case the description isn’t entirely clear. Don’t forget to sign up for my YouTube channel!

Put Together Your Unicorn Cupcakes

Use this rainbow swirl design on unicorn cupcakes with printable wrapper and toppers or make the unicorn cupcake cake:

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Unicorn cupcake cake with rainbow swirl frosting. Cupcake wrapper has sleepy eyes and topper has a horn with flowers.

I used a white cake mix for these easy vanilla cupcakes.

Although a box mix will do, you may want to try this quick and easy vanilla birthday cake recipe or my moist chocolate cake recipe to make your unicorn cupcakes.

The unicorn horn with unicorn ears and flowers, and the wrapper with the eyes are printables available in my shop.

Truly Magical Unicorn Birthday Party Decorations DIY - By Press Print Party!

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How to Store Your Unicorn Frosting

If you want to plan ahead, you can either:

Method 1 – Store frosting separately

  • Make all 4 frosting colors and store them in their separate bags in the fridge or a cool place. (I like to stand them up in a glass).
  • The day of the party (next day or up to a month later), warm them up to room temperature on the counter.
  • Make the rainbow frosting as instructed.
  • Pipe rainbow swirls on your unicorn cupcakes.


Method 2 – Store already made

  • Prepare the rainbow frosting bag with all 4 colors and store it in the fridge right away before it gets too warm (Standing up in a glass)
  • The day of the party, warm it up on the counter to room temperature.
  • Use your unicorn frosting to pipe swirls on your cupcakes.

Either way will work. I like the first method best because I think you get sharper colored lines that way. The different frosting colors don’t have the opportunity to melt together.

But if you need speed on the day of the party, method 2 is for you.

The leftover frosting should be stored in the fridge for no more than a month. But you can freeze your buttercream frosting for up to 3 months in an airtight container.

Rainbow cake frosting is really a simple technique once you’re shown how to do it.

It’s also fun to change up the combination of colors for any event like soft pinks and blues different colors of icing for baby showers and gender reveal parties. Or more colors of the rainbow for St. Patrick’s day. You can also choose matching bright colors for birthday parties.

Let your imagination think up all kinds of rainbow desserts in all kinds of various colors.

Don’t forget to check out the recipe card for my foolproof Swiss meringue buttercream frosting. I promised you it tastes better than the typical American buttercream icing.

Don’t forget to pin this unicorn rainbow frosting for easy unicorn cupcakes:

DIY Rainbow Swirl Frosting (Unicorn Cupcakes) make your own rainbow frosting for unicorn cupcakes- Press Print Party!

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9 thoughts on “How to Make a Stunning Rainbow Frosting Swirl (Unicorn Cupcakes)

  1. Melissa R says:

    Can I make the frosting the night before I plan to put it on the cupcakes? Like keep the colors separate overnight. Then the next day let it warm enough to pipe the stripes?

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