The 'Cosmopolis' star was captured on camera shoving a guy, who he mistakenly thought was a photographer, out of his way after enjoying a few drinks with two friends at the Troubadour nightclub in West Hollywood, Los Angeles on Friday.
The 27-year-old British actor was swarmed by paparazzi as he made his way into a waiting vehicle outside the hotspot, despite being surrounded by security, and suddenly threw his hand towards a man's face in the crowd, pushing him backwards and knocking his glasses off his face.
The incident was captured on camera by gossip website TMZ.com and the victim, who is part of the club's security team, can be heard saying: "He grabbed me on my face," as he picked up his glasses.
But he quickly brushed off the incident, adding: "He (Robert) thought I was somebody else."
A source close to the 'Twilight Saga' star told HollywoodLife.com that Robert has been miserable since splitting up with Kristen Stewart.
The insider said: "Rob is missing Kristen like crazy. He thought by moving to Beverly Hills and hanging out with his new friends it would take his mind off Kristen, but it has done the complete opposite. His distractions are only making him miss Kristen more.
"He is lonely and sad. He's in a new home, but it doesn't matter, having Kristen not around isn't the same. He used to laugh with Kristen and things just aren't the same with her not around."