The Keeping Up With the Kardashians star took to Instagram on Saturday to share photos from the elaborate dinosaur-themed party, which included jungle decor, a ball pit, an area to dig for fossils and more.
"Look guys! Saint's dinosaur party is today," Kim shared on her Instagram Story. "How cute is everything? We are still setting up."
Saint adorably turned away from the camera in a few shots, but couldn't hide his smile after finding a dinosaur mask to sport during the party. He sweetly comforted little sister, Chicago, after the mask had her running to her mom in fear. Saint's big sister, North, was also in attendance at the party, as was his little brother, Psalm.
Kim shared a touching message in honor of Saint's birthday on Thursday.
"I have no words to describe how much I love your smile and those curls of yours Saint!" she began her post on Instagram. "You bring so much joy into my soul. You are so kind, loving and just so thoughtful and sweet! I am so happy today if your 4th birthday and We get to celebrate how much you’ve grown!"
Kim continued, "Happy birthday my sweet sweet Sainty. (When I say to him my sweet sweet Sainty, he says back to me my sweet sweet sweet sweet Momma, the best momma in the world and the only momma I ever want! HOW CAN YOU NOT MELT AT HIS SWEETNESS)."
See more on the family in the video below.