McConaughey's representative confirmed that his wife is pregnant with the couple's third child. Both the actor and his bride tweeted the news on Wednesday.
"Happy birthday America, more good news, Camila and I are expecting our 3rd child," the actor wrote, "God bless, just keep livin."
The baby will join a son named Levi, who turns 4 this week, and 2-year-old daughter Vida.
McConaughey, 42, wed 29-year-old Brazilian-born Camila Alves last month in a ceremony at their Austin, Texas home.
Camila McConaughey, as she is now known, is a handbag designer and model who will begin appearing in Macy's ads next month. Matthew McConaughey has been busy promoting his new film "Magic Mike."