Patton, 33, is pregnant, according to a message posted on Facebook by Thicke's mother, former soap opera star Gloria Loring.
"I am going to be Nana Gloria again as my son Robin Thicke & his wife Paula are expecting their first baby!," Loring wrote.
This will be the first child for the high school sweethearts, who married in June 2005.
Last year, Thicke, 32, said that there was "a 100 percent chance" of starting a family with his wife, "just not right now. We're still little kids ourselves in some ways!"
Patton's new movie, Precious, hits theaters Nov. 6, while Thicke's latest album, Sex Therapy, will be released Dec. 8.