Samuel L Jackson urged American voters not to be "tricked like they got tricked in London" as he was honoured at the Black Entertainment Television (BET) Awards.
The actor's comments - an apparent reference to the EU referendum - came as he received the lifetime achievement award at the show in Los Angeles.
Jackson praised Grey's Anatomy actor Jesse Williams, who launched a rousing speech about racial injustice after he picked up the humanitarian award.
The Pulp Fiction star described Williams as "the closest thing I've heard to a 1960s activist", adding: "That brother is right and he's true, and when you hear what he said, make sure you vote and you take eight more people with you to vote, OK? Don't get tricked like they got tricked in London."
Williams, 34, received a standing ovation after he used his six-minute acceptance speech to call for an end to police brutality against black people and white appropriation of black culture.
"A system built to impoverish, divide and destroy us cannot stand if we do," he said. "We know that police somehow manage to de-escalate, disarm and not kill white people every day.
"We're done watching and waiting while this invention called whiteness uses and abuses us, burying black people out of sight and out of mind while extracting our culture, our dollars, our entertainment like oil, black gold, ghettoising and demeaning our creations then stealing them; gentrifying our genius and trying us on like costumes before discarding our bodies."
A host of artists including Stevie Wonder and Jennifer Hudson paid tribute to the late music superstar Prince with a series of performances at the awards. Prince's ex-fiancee Shelia E and his former wife Mayte Garcia were among those to honour the Purple Rain star, who died of accidental overdose in April.
Muhammad Ali was also remembered at the show in the Microsoft Theatre, with actor Jamie Foxx and Ali's daughter Laila paying tribute to the three-time world heavyweight boxing champion.
Beyonce made a surprise appearance at the awards, performing Freedom featuring Kendrick Lamar, before leaving the ceremony to travel to a concert in London.
After winning video of the year and the viewers' choice award for her song, Formation, Beyonce's mother Tina accepted the awards on stage and said: "I want to thank, first of all, her husband and her daughter."
Drake, who did not attend the show despite receiving nine nominations, won best male hip hop artist and best group with rapper-singer-producer Future.
Ali's daughter Laila fought back tears as she paid tribute to her father, who died in June after a long battle with Parkinson's disease.
"To me and my eight sisters and brothers, he was just dad," she said. "My father also once said, 'If people loved each other as much as they loved me, it would be a better world.'"
The award show airs in the UK on BET on Tuesday at 9pm.