"As many of you may know, our son Jack was just over 3 pounds when he was born," he wrote on Instagram of his son with wife Anna Faris. "Thanks to scientific advances made possible by #marchofdimes funding, today he's a perfectly healthy, curious 4 year old."
"Today is #worldprematurityday. 15 million babies are born #prematurely each year around the world. And 1 million of them won’t live to celebrate their 1st #birthday," Pratt continued. "The @marchofdimes strives for a world where every #baby has a fair chance, yet this is not the reality for many mothers and babies."
"Join me in supporting their efforts to give every baby a fighting chance by clicking the link in my bio," he sweetly concluded. "Thank you!"
We just can't get enough of Jack and his parents -- and hopefully we'll be seeing a lot more of the adorable family while Pratt takes some time off.
The 37-year-old actor recently revealed that he would be taking a six month break from acting projects to spend more time with his family.
"I've been on the road for 14 months -- I did three movies back to back to back -- so I'm taking six months off," he told Parade magazine. "I'm taking Jack to Jack's Beach -- which is what we named the little stretch of beach on an island up on the San Juan Islands where we got a place. We're going to go back to the fort we built about a month and a half ago when we went for a short visit and see if that's still there. If not, we're going to build it again."
The Jurassic World star will also be spending plenty of time with his wife -- opening up to ET in September about his rules when it comes to romance.
"I have heard some people say 'Don't go to bed mad.' I think that is garbage. Sometimes you've got to go to bed mad," he noted, adding, "but at least touch toes, you know what I mean? At least touch toes. 'We will deal with it later. I think I am going to get some sleep,' and touch toes."