Police were called on Jack Osbourne after the star punched his estranged wife's new boyfriend in the head, according to a report.
The reality star, 32, was reportedly left furious when the new man showed up at the home he shares with wife Lisa as he tried to work on rebuilding their relationship.
Lisa filed for divorce in May just months after their third child Minnie was born.
TMZ reports that police went to the home, and a battery report was filed. It added that the boyfriend hasn't pressed charges, and Jack proved uncooperative with the police.
"The Osbournes" star, who is currently working on "Ozzy and Jack's World Detour!" with his dad, is said to be committed to winning Lisa back.
A representative for Jack has yet to comment.