"The Hills" stars welcomed their first child together, a baby boy named Gunner Stone on October 1, reported Us Weekly.
The couple announced the news in a statement to the magazine, which read, "Heidi and Spencer are proud parents of a healthy baby boy as of this afternoon."
Montag, 31, said she was equally excited and scared to be a new mother.
"We are so blessed to have a beautiful healthy baby boy. It was the hardest and most rewarding experience," she said.
While Pratt described the experience as, "Officially the most lit day of my life."
Montag and Pratt started dating on the 2006 show "The Hills" and eventually tied the knot in 2008.