"After nine months of intensive development, Team Downey is pleased to announce our 2014 fall/winter project," the post reads. "Principal photography commenced 11-14 and will continue until she says, 'Dad! You are embarrassing me ...I'm 30, this has gotta stop.'"
All jokes aside, the baby announcement continues, "Yep ...Avri Roel Downey joined the party at 3:22 a.m. on November 4th ...She's 7 lbs. even, spans 20 inches, and is accompanied by a variety of Susan's traits that have seemingly overwritten my 'junk DNA.'"
RDJ assured his fans, "I'll post pics here + there when I'm not too busy staring."
This is the couple's second child. Their son Exton was born in February 2012, and the 49-year-old actor also has a 21-year-old son named Indio from his previous marriage to singer Deborah Falconer.
Susan, 40, is a film producer and works with her husband on their production company Team Downey. Recently, the two showed off her growing baby bump as they did press for their film The Judge, which RDJ plays the leading man.
The A-lister opened up to ET's Rocsi Diaz about his fears and concerns with raising a daughter. "I don't want to be a pushover. I hear about these pushover dads," he said. "I want to be a fair but firm dad. I want her to fear and respect me."
Susan admitted that being a mother to a young son hasn't necessarily prepared her for raising a daughter.
"I have no idea what to do with a little girl," she said. "For some reason I understand little boys because I grew up with two brothers. This is going to be a fun adventure for both of us."
Check out the video below for more from RDJ and his wife on their plans for parenting a baby girl.