The British awards, known as BAFTAs, are considered a portent of success at Hollywood's February 28 Academy Awards, where DiCaprio is also a nominee.
The role of a fur trapper fighting for his life has earned DiCaprio his sixth Oscar nomination and, many believe, his best shot at finally winning.
Alejandro Gonzalez Inarritu's "The Revenant" has eight BAFTA nominations, and took an early prize for Emmanuel Lubezki's cinematography.
The best-picture nominees are "Bridge of Spies," ''Carol," ''The Revenant," ''Spotlight" and "The Big Short." DiCaprio is up for best actor against Matt Damon for "The Martian," Bryan Cranston for "Trumbo," Fassbender for "Steve Jobs" and last year's winner Eddie Redmayne, nominated for playing a transgender artist in "The Danish Girl."
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The best-actress category pits Alicia Vikander for "The Danish Girl" against Brie Larson for "Room," Blanchett for "Carol," Maggie Smith for "The Lady in the Van" and Ronan for "Brooklyn."
Among the arrivals were nominees DiCaprio, Mark Ruffalo, Michael Fassbender, Cate Blanchett, Saoirse Ronan, Kate Winslet, Steven Spielberg and "Star Wars" action hero John Boyega.
A group called Creatives of Colour Network organized a protest beside the red carpet against a lack of racial diversity in show business. Demonstrators rallied under the hashtag #baftablackout, and distributed leaflets declaring the awards "male, pale and stale."
The movie awards season has been dominated by debate about why the film industry remains dominated by white men. All the acting nominees for the Oscars both this year and last have been white.
The head of the British film academy said she supported today's protesters.