In April, Gibson's wife Robyn filed for divorce after 28 years of being married to the star, and she said there were irreconcilable differences between them both.
Mel Gibson was recently seen in public at a Hollywood premiere with 39-year-old Grigorieva and it looked as if they were going out together as a couple.
Gibson told the American chat show host that the situation with his wife Robyn was "unfortunate" and he explained that their marriage came to an end "three years ago."
Mel Gibson already has seven children by Robyn so the child that Grigorieva is expecting would be his eighth.
