Three-Rex Cake (Easy Dinosaur Birthday Cake Tutorial)

A Three-Rex themed third birthday is such a fun idea for any child who loves dinosaurs! Making your own cake is a great way to help turn your child’s special day into a themed party and impress your little guest of honor and their friends.

This three-rex birthday cake looks like so much fun and is incredibly easy to make, even for a total beginner. All you’ll need is some small toy dinosaurs, cookies and frosting to make a chocolate cake come alive! 

How to make a three rex cake for a dinosaur birthday

To make this easy dinosaur birthday cake, you can use your favorite chocolate cake mix or chocolate cake recipe. Making the cake in a glass pan makes it easier to decorate if you’re unsure of your frosting skills. Alternatively, you could make this into a dinosaur sheet cake by baking chocolate cake sheets and layering them.

Follow along with these photos and instructions, there’s also a printable recipe card at the end of this article you can skip to here if you’d like.

Bake your dinosaur birthday cake

A chocolate dinosaur birthday cake looks like earth or mud under the dinosaur’s feet when you cut into the cake and decorate it. Decide if you’re baking from scratch and follow the recipe or use a box of chocolate cake mix. If you’re baking from scratch, you might want to try this recipe for Chocolate Fudge Cake.

Make sure you allow your cake to cool completely before you decorate it. You can even bake the cake the night before your dinosaur themed birthday party and cover it, then you can decorate it the next day.

Carve a number three in the birthday cake

For a three-rex birthday cake, use some wax paper the same size as your cake and draw a three on it for a 3rd birthday party. You can also make a ‘roar-four birthday cake’ or any other number you’d like. It will look great. 

number three for birthday cake

 I used wax paper and a permanent pen to draw my outline, cut it out with scissors and then placed it on my cake to cut around. This will give you a nice shape to trace so there is no guess-work in how it will look. 

number three on cake with green frosting and dinosaur toys to the side

Once you’ve traced your number outline, use a thin spoon to scoop out the top layer of cake inside the lines of your number. You don’t have to go very deep.

number three carved into cake

Add crushed oreos for a dinosaur dig site cake

To make the number three on your three-rex cake stand out, add some crushed oreo cookies, which will look like a dinosaur dig site cake. You could add chocolate dinosaur bones or toy dinosaur bones to the dig site if you’d like. You can use biscoff cookies for brown dirt instead of oreo cookies for black dirt. 

Alternatively, you can also fill the number three with blue icing to make it look like a dino land cake or a Jurassic dinosaur cake with a blue pond or river. 

Green frosting dinosaur cake

If you have many shades of food coloring to play with, try using one drop of yellow, one drop of blue, and one drop of brown to get the same shade of green you see in my photos. Adding a tiny bit of brown will give you a slightly more sophisticated sage green color. But a bright shade of green frosting for a dinosaur cake is also a great idea; it will look like eye-catching grass. 

green frosting on dinosaur cake for three year old

I used a star tip with my piping bag, but you can use a grass-tip. You can also use a rubber cake spatula to spread your icing carefully around your three-rex cake. Take extra care around the edges of your number so they don’t tear. 

Toy dinosaur sheet cake decorations

Last but not least, it’s time to add decorations to your dinosaur sheet cake. Whether you made your cake in a glass pan or you used sheets of chocolate cake, you can add some small dinosaur toys on top of the cake.

toy dinosaur sheet cake with number three in it

I also got a plastic fern branch and broke it up to use it as part of the cake decorations. Dinosaurs are so popular that wherever you buy supplies for your birthday parties, it is almost guaranteed to have some great little toys that fit your dinosaur theme. You can also find toy dinosaurs on Amazon.

Dinosaur cake topper ideas

You can use small plastic dinosaur toys on the top of your three-rex cake (be sure to wash them well before using). You could also use small plastic plants or break up a larger plastic fern for decoration. In the photos below you can see what the cake looks like if you use some mini-eggs to look like a dinosaur egg cake topper.

easy three rex birthday cake

You can buy custom three-rex cake toppers from Amazon or Etsy if that’s your preference! It is possible to get a non-dinosaur themed 3rd birthday cake topper for this cake, which will look great too.

roar I'm four birthday cake

How to make a dinosaur cake at home

This is by far one of the easiest ways to make your own dinosaur cake at home with a total beginner skill level. It will save you a lot of money instead of buying a custom dinosaur birthday cake and it still looks super exciting for your three year old birthday boy or birthday girl. 

  • Ingredients
    • Box of chocolate cake mix
    • Three eggs
    • ½ cup oil
    • 1 ¼ cup water or milk
    • One can of white frosting 
    • Green food coloring
    • Oreo cookies
  • Materials
    • Electric mixer 
    • Icing tips
    • Icing bags
    • Cake pan
    • Bowls
    • Spoons
    • Rubber spatula
    • Wax paper
    • Permanent marker
    • Scissors 
    • Small dinosaur toys
    • Plastic plant leaf
three rex dinosaur birthday cake

Three-Rex Birthday Cake

How to make your own easy Three-Rex cake for a dinosaur themed birthday at home!
No ratings yet
Prep Time 1 hour
Cook Time 30 minutes
Total Time 1 hour 30 minutes
Course Dessert
Cuisine American
Servings 16
Calories 250 kcal


  • Electric mixer
  • Icing tip grass tip or star tip
  • Icing bags
  • Cake pan
  • bowls
  • spoons
  • Rubber spatula
  • Wax paper
  • Permanent marker
  • Scissors
  • Small dinosaur toys
  • Plastic plant leaf


  • 1 Box of chocolate cake mix
  • 3 Eggs
  • ½ cup Oil
  • 1 ¼ cup Water or milk
  • One can of white frosting
  • Green food coloring
  • 6 Oreo cookies


  • Bake your cake according to the box cake instructions.
  • Cool cake completely.
  • Use wax paper to draw a number 3 you will use as a stencil to trace onto your cake. Cut out the number 3 with scissors and place it on top of your cake. Trace the number 3 onto the top of your chocolate cake with a sharp knife.
  • Carefully dig out the inside of your number three cake. Just dig out a shallow small amount of the chocolate cake.
  • Scrape out the cream from 6-10 Oreo cookies. Put the black cookie part of the Oreos in a ziploc bag and crush them, or crush them with your food processor. Sprinkle the cookie crumbs into the cut-out 3 on your cake.
  • Mix green food coloring with your white frosting. Or mix one drop of blue, yellow, and brown together for the same color seen in my photos. Put the icing in a piping bag with a star tip or grass tip and cover the surface of your cake surrounding the 3.
  • Decorate the top of the cake with small dinosaur toys and plastic leaves. Optionally, add mini chocolate eggs as 'dino eggs'.


Calories: 250kcal
Keyword Cake, Dessert

More easy birthday cake ideas

2 thoughts on “Three-Rex Cake (Easy Dinosaur Birthday Cake Tutorial)”

  1. Pingback: 31 Amazing Dinosaur Cake Ideas - Good Party Ideas

  2. Pingback: No Bake Mini Oreo Cheesecake

Leave a Comment

Your email address will not be published. Required fields are marked *

Recipe Rating

%d bloggers like this: