"Today is my dad's birthday. I know there's nothing more in the world he would have wanted than to meet his grandchildren. So I wanted to share this pic of Saint with you all," Kardashian, 35, captioned the sweet photo of the baby boy.
In the shot, Saint has his tiny arms raised in the air and is wearing a white long-sleeve shirt.
This is the first official image of Kanye West's son that has been released since he was born on Dec. 5. Kardashian previously posted a photo of her daughter North West's hand holding Saint's tiny finger.
"She said, 'He's my best friend,'" the reality star captioned the photo.
Kardashian's father, Robert Kardashian, passed away in September 2003 after a battle with cancer. His name has recently been back in the news as David Schwimmer portrays him in the FX event series, The People v O.J. Simpson: American Crime Story.
In a separate post on her website, Kim honored her father's birthday, writing, "Happy Birthday dad! I can't believe you would have been 72 today. So much has gone on in our lives since you've been gone and I know you have been my guardian angel seeing everything unfold! I love and miss you so much!"