Carrey's 23-year-old daughter Jane and her then-husband Alex Santana welcomed their first child last February.
Jane and Santana announced plans to divorce months later in December 2010, but promised to retain a friendly relationship for the sake of their son.
Mr. Popper's Penguins star Carrey has now opened up about his own bond with 1-year-old Jackson Riley, acknowledging that the boy's birth changed his life forever.
Carrey told Access Hollywood: "When [he was born], oh my gosh, it was just like an explosion of pure bliss… He is the coolest dude on earth, unless he gets tired and then he's a marauding maniac… What a fantastic thing! He's so clued in and we play soccer together and he's really co-ordinated, it's amazing."
The 49-year-old also joked that he has already set lofty goals for his first grandchild, saying: "I'm the grandfather that wants to improve him and stuff like that. I say, 'Start reading to him right now! While he's playing soccer! He must be a super being!'"
Carrey donned a green screen suit during an appearance on last night's 2011 MTV Movie Awards.
