The father-of-six was struck in the face on Wednesday night (28 May) while on the red carpet in Hollywood, confirm the Los Angeles Police Department.
Angelina was on another part of the carpet at the time.
According to reports, the culprit was a notorious celebrity 'prankster', who has a long history of approaching stars with odd behaviour.
He's accused of jumping the security barriers at the El Capitan Theatre and making contact with Brad, before security intervened.
Brad was not hurt.
The 25-year-old suspect was arrested and booked on suspicion of misdemeanour battery. Witnesses told The Hollywood Reporter that he either punched or slapped Brad before being whisked away.
A spokesperson for Disney told Variety: "This was an unfortunate and inappropriate incident that is being investigated by the LAPD."
It's not the first time his bizarre antics have made headlines.
Just this month he left Ugly Betty star America Ferrera looking distraught after trying to climb under her voluminous dress at the Cannes Film Festival. He also got a slap from Will Smith on another red carpet after trying to kiss him.
Other stunts have included dropping to his knees to hug Leonardo DiCaprio, and attempting to crash the stage at the Grammy Awards after Adele won last year.
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