The actor has reportedly welcomed a baby daughter, his first child with girlfriend Oksana Grigorieva, the site reported.
The baby reportedly arrived a few weeks early from the Russian singer's December due date.
Mel's longtime rep had no comment on the report when reached by Access Hollywood.
Mel has seven children with his estranged wife, Robyn, who filed for divorce in April.
Mel stepped out publicly with Oksana shortly thereafter.
He confirmed her pregnancy on "The Tonight Show" in May, explaining to then-host Jay Leno that he and Robyn had been separated for "three years."
"I guess I'm Octo-Mel," he joked at the time.
While RadarOnline reported Mel and Oksana as engaged, the singer said during an appearance on Britain's "GMTV" in September that the couple had no plans to walk down the aisle.
"We have no plans whatsoever. I haven't thought about it – we haven't spoken about it," she said at the time.
The new baby is the second child for Oksana, who has a 12-year-old child with former "James Bond" star Timothy Dalton.