"Having a daughter in May," Wolf tweeted on Wednesday. "She will own me. I'm already mad at the boys. No words could express how full our hearts are. Luckiest guy I know."
Wolf, 45, is already a dad to sons Jackson, 4, and Miller, 1. He and Kelley, a Real World: New Orleans alum, have been married since 2004.
Wolf's TNT drama Perception returns on Tuesday, Feb. 25 at 10/9c.