Dean, who alongside singer Lola Young led nominations with five nods each, triumphed in the first award of the night, song of the year, for Rein Me In, a collaboration with rocker Sam Fender.
The 26-year-old, known for her soulful voice and music that blends R&B, pop and neo-soul, won pop act, artist of the year and album of the year for her second studio album, The Art of Loving.
"Making this album has changed my life," said Dean, who earlier this month won best new artist at the Grammys.
"This album is just about love and loving each other in a world that feels lovelessness right now."
Fender also won alternative/rock act, while Messy singer Young won breakthrough artist.
Rock band Wolf Alice won group of the year. In her acceptance speech, singer Ellie Rowsell thanked "all the pubs, clubs and grassroots venues across the country where we quite literally learned to play our instruments and write our songs".
Organisers announced several winners ahead of Saturday's ceremony, with Noel Gallagher named songwriter of the year and PinkPantheress crowned producer of the year.
At 24, she is the youngest ever and the first woman recipient of the prize.
Ozzy Osbourne, the late frontman of heavy metal band Black Sabbath, was honoured with a lifetime achievement award. "The Prince of Darkness" died in July aged 76, around two weeks after Black Sabbath's emotional farewell gig.
"Ozzy was authentic, he was gifted, totally unpredictable, a wild man, he was a true artist," Osbourne's wife, Sharon Osbourne, said before singer Robbie Williams performed a musical tribute.
Among the international category winners was singer Rosalia, who won international artist of the year.
"I would love to share this with all my peers who also make music in Spanish," Rosalia said. "Let's keep celebrating the otherness, let's keep celebrating different music, different cultures, different languages."
This year's BRITs took place in the northern English city of Manchester, the first time the awards ceremony was held outside of London.
with Reuters
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