Rainbow Cupcakes with Marshmallow Buttercream

5 from 1 vote

These adorable Rainbow Cupcakes never fail to please! Everyone will think you spent hours making them, but the cupcakes are made with cake mix and couldn’t be easier.

Each cupcake has layers of vibrant colors and is topped with pillow-soft homemade marshmallow frosting. Plus, I’m showing you how to top a rainbow cupcake four different ways. These easy rainbow cupcakes are perfect way to celebrate!

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Rainbow cupcakes with marshmallow frosting

I am IN LOVE WITH RAINBOWS! I have been for years, even before they became so popular in recent years. Around my 35th birthday I declared that my 40th would be a rainbow party – and it was! My office is even decorated with unicorns, rainbows and, of course, lots of sprinkles!

I have been making this rainbow cupcake recipe for years and they always bring a smile to everyone’s faces. They’re great for birthday parties or any time you want to celebrate.

When I’ve made them for events, I’m always asked how many hours I spent making them because all of those rainbow colors layered together look really complicated. Here’s my secret: they don’t take hours to make because I use boxed cake mix to make them. And, creating those colorful layers isn’t hard it at all! 

Rainbow cupcakes with sprinkles

People always assume they’re homemade and I think it’s the soft marshmallow frosting that makes the difference – pairing a homemade frosting with boxed cake mix is a great way to make it seem like all of it’s homemade. It’s a great trick to have up your sleeve.

Pair a homemade frosting with a cake mix cupcake and everyone will think they’re homemade!


So, in this post I’m showing you how to make the rainbow cupcakes and the from-scratch marshmallow frosting. Plus, I’ll share four different toppers to decorate them. So, I gotta ask – are ready for some rainbow fun?

Rainbow cupcakes process

How to Make Rainbow Cupcakes

For the cupcake base you’ll need a boxe of white cake mix. Normally cake mixes make about 18-24 cupcakes but with all of the coloring and transferring of dishes, these make about 12-14.

I recommend using white cake mix because you’ll get very vibrant colors. Yellow cake mix is, well, yellow, and will muddy the colors of the food coloring.

Just mix up the cupcake batter following the instructions on the package. Once it’s made, divide it evenly among six bowls.

Food Coloring for Cupcakes

Once your batter is divided it’s time to create the colors. I like to use gel food coloring because the colors always turn out extra bright and pretty. For the colors, you’ll need red, orange, yellow, green, blue, and purple.

Add one color to each bowl and stir until the color is evenly distributed in the batter. To make it easy to create the cupcake layers, transfer each batter to its own Ziplock bag and snip off one corner so you can squeeze the batter through it.

Now we’re ready to create the layers. To create a rainbow, you will want to layer the colors in this order:

  • Purple
  • Blue
  • Green
  • Yellow
  • Orange
  • Red

So, start with the purple batter and squeeze a small amount into the bottom of each cupcake liner in the pan. You only need enough to cover the bottom of the liner. Repeat this process, layering a small amount each color on top of each other.

Once you’ve created all of the layers bake the cupcakes according to the package directions. Cool them completely before you decorate them with frosting and rainbow cupcake toppers.

Marshmallow frosting step by step

Homemade Marshmallow Frosting

Once your cupcakes are cooled, they are ready for decorating. I love marshmallow frosting for these because it looks like a cloud. I always like to imagine clouds taste like marshmallows, don’t you? Plus, the rainbow and cloud combo is just too cute.

Homemade frosting makes cake mix cupcakes taste homemade! Here’s what you need to make the frosting:

  • Softened unsalted butter
  • Jarred marshmallow crème/fluff
  • Powdered sugar
  • Vanilla
  • Pinch of salt

Cream the butter with the marshmallow crème until well combined. Add the vanilla and powdered sugar and beat together. Transfer the frosting to a piping bag and pipe the it onto each cupcake so it looks like a puffy white cloud.

Rainbow cupcakes with rainbow topper

Four Different Toppers for Rainbow Cupcakes

What I love about these cupcakes is that there are several different ways to decorate them. These are my favorite rainbow cupcake toppers, but feel free to experiment!

  • For a simple decoration just top them with the marshmallow frosting – totally cute that way!
  • Or, add some rainbow sprinkles to dress them up a little. So easy.
  • You can also top the frosting with an Airhead Extreme which is a chewy rainbow-colored candy. Just lightly press one end into the surface of the cupcake, bend it into an arch and secure the other end in the cupcake so it looks like a little rainbow.
  • You can create a mini “cupcake” decoration by topping the frosting with a mini white chocolate peanut butter cup. Add a dollop of frosting on top with some sprinkles.

They are almost too cute to eat! Almost. You’re going to want to take a bite just to see that beautiful rainbow inside. I hope you love them as much as I do!

Rainbow cupcakes with cupcake topper

Other rainbow and unicorn desserts:

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Rainbow Cupcakes Recipe

These are my favorite EASY Rainbow Cupcakes! Start with a box mix for the cupcake but make a homemade marshmallow buttercream frosting and FOUR different ideas for topping!
5 from 1 vote
Prep Time 30 minutes
Cook Time 20 minutes
Total Time 50 minutes
Yield 12 cupcakes
Serving Size 1 cupcake


For the Rainbow Cupcakes

  • 1 15 ounce box white cake mix , prepared with eggs, oil, and water called for on the box
  • Food coloring (red, orange, yellow, green, blue, purple (gel food coloring works best for vibrant colors)

Marshmallow Buttercream

  • ½ cup unsalted butter softened
  • 1 7 ounce jar marshmallow creme
  • 1 ½ cups powdered sugar
  • 1 teaspoon vanilla
  • Pinch salt

For the Cupcake Toppers

  • 24 white chocolate Reese's Peanut Butter Cups or
  • 12 Airheads Extremes cut in half, or
  • rainbow sprinkles


Make the Cupcakes

  • Mix the cake batter according to the recipe or box directions. Line your muffin tins with cupcake liners.
  • Divide your batter evenly among six bowls. Add food coloring to each bowl, one for each color of the rainbow (red, orange, yellow, green, blue, purple). Stir to combine.
  • You are going to layer the cupcakes into the liners in a reverse rainbow, so the purple is on the bottom and the red is on the top. To make this easier to do, place each color in a separate quart-sized Ziploc bag. Seal the bag almost all the way, leaving about ½″ open for air to escape. Snip off a tiny corner and place a small amount in each cupcake liner, starting with purple (use just enough to cover the bottom of the liner). Repeat with the remaining colors in this order: blue, green, yellow, orange, red.
  • Bake according to box directions. Let cool completely.

Make the frosting

  • Beat butter and marshmallow creme together until smooth, then mix in powdered sugar, vanilla and salt. Frost cupcakes as desired (I like using a 1M tip).

Topping the cupcakes

  • Leave plain with the frosting.
  • Add rainbow sprinkles.
  • Place an Airhead Extreme in a rainbow arch on top.
  • Place a white chocolate peanut butter cup on top, frost it with frosting and sprinkle with sprinkles (like it's a mini cupcake ton top).
  • Store cupcakes in refrigerator to set frosting (it's a bit fluffy and will collapse if it's not set).

Recipe Video

Nutrition Information

Serving: 1cupcake | Calories: 128kcal | Carbohydrates: 15g | Protein: 1g | Fat: 8g | Saturated Fat: 5g | Cholesterol: 20mg | Sodium: 2mg | Sugar: 15g | Vitamin A: 236IU | Calcium: 2mg

Nutritional information not guaranteed to be accurate

Course Dessert
Cuisine American
Keyword cupcake, rainbow
Rainbow cupcakes collage

Rainbow Cupcakes with marshmallow frosting are such a fun and easy way to celebrate! These DIY cupcakes use a cake mix but have a homemade marshmallow buttercream. Learn how to make rainbow cupcakes with 4 different decoration toppers!

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11 CommentsLeave a comment or review

  1. My family loved it, my nephew had 3 cupcakes in one day!! Everybody loved them they wanted more cupcakes.

  2. Dorothy,
    Love the toppers! So cute! 🙂 I’ve made these cupcakes for a few years and love them! 🙂

  3. What a fun idea! And I agree, they grow up too fast (and not fast enough, sometimes…). My older daughter is going to be six in about two months, and I’m having a hard time coming to terms with that!