Black himself announced the arrival during Monday's Hollywood premiere of his new comedy Nacho Libre, telling TV's Access Hollywood, "Secretly, between you and me, it's already happened. I've got the babe back at home safe and sound, and I'm actually very anxious to get back to my lovin's (loved ones)."
Indeed, Black left the premiere shortly after the lights went down and the screening began.
"I think I will be good when it comes to playtime," he told reporters, according to USA Today. "I don't know how good I'll do with the discipline."
Black, 36, and Haden, 34, first met as students at Crossroads, a private high school in Santa Monica, Calif., and started dating in April 2005. They exchanged vows in a private ceremony in Big Sur, Calif.
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In September, Black is set to begin filming Be Kind, Rewind, costarring Kirsten Dunst.
"Wherever the job goes, the baby is just going to come with me," he said last month. "It will work out." Besides, he joked, "I don't really get involved until he's, like, 10."