When TV host Jay Leno questioned the star - who is in the middle of a multi-million divorce with his estranged wife Robyn - about reports Russia-born singer Okasana was pregnant, Mel replied: "This is true. We're going to have a child."
The Aussie actor, who already has seven children aged ten to 26, then joked. "I guess I'm octo-Mel."
Though clearly happy to confirm the news, Mel gave away few details about the baby during his segment on the The Tonight Show With Jay Leno. When asked about the baby's gender, he responded, "A human being, I think."
The new arrival with be the second child for Okasana, who is signed to Mel's record label Icon. The 39-year-old - who is reportedly in the third trimester of her pregnancy - already has a teenage son with former James Bond star Timothy Dalton.
During his appearance on the chat show, Mel also discussed the break down of his marriage, which he says ended three years ago. "These things happen. It's unfortunate, it's sad, but you know (Robyn) is an admirable woman - we've still got kids together. We're friends."
When pressed on what went wrong he replied: "Look. When it's all said and done, I did a pretty good hatchet job on my marriage myself. I'm to blame. If you're inclined to judge, put it here."