The Hunger Games star allegedly confronted another man after believing that he had thrown a rock at him and his friend, TMZ says.
Unclear footage of the altercation hosted by the website appears to show Hemsworth and his acquaintance holding the man down on the ground.
The disagreement came to an end when the police arrived to break it up, although no arrests were made.
Meanwhile, the other man involved - who identified himself as Rob and seemed to have blood on his face after the row - has reportedly not filed a police report about the incident.
Hemsworth proposed to his girlfriend Miley Cyrus earlier this year, though Cyrus has denied rumours that the couple have set a date for the wedding.