Mars left with six trophies in all, including the three biggest prizes: Album of the year, song of the year and record of the year.
Speaking onstage, he paid tribute to his fellow nominees, saying: “You guys are the reason why I’m in the studio pulling my hair out”.
He also told the story of how, as a 15-year-old in Hawaii, he performed in a show called The Magic of Polynesia, singing songs by R&B writers Babyface, Jam & Lewis and Terry Riley.
“I’ll be honest, I was incredible at 15,” he laughed, before explaining how he’d wanted to recapture the sounds of those 80s and 90s hits on his latest album.
“Those songs were written with nothing but joy… and that’s all I wanted to bring with this album. Hopefully I could feel that again and see everybody dancing and everybody moving.”
As well as the star’s own prizes, his recording engineers won a further award for their work on the album.
His victory robbed Kendrick Lamar’s more urgent, political album of the night’s main prizes – but the Compton-born star still took home five trophies, including best rap album, best rap song and best rap performance.
He also opened the ceremony, in New York’s Madison Square Gardens, with a provocative, politically-charged performance that featured contributions from U2 and Dave Chapelle.
“I just wanted to remind the audience that the only thing more frightening than watching a black man be honest in America is being an honest black man in America,” observed Chapelle in the middle of the segment.
Lamar’s victories came at the expense of rap veteran Jay-Z and his soul-baring album 4:44.
Jay-Z won none of his eight nominations and chose not to perform at the three-hour show. But Lamar tipped his hat to the elder star, declaring “Jay for president!” as he collected the best rap album award.
The night also saw performances from Lady Gaga, Sam Smith, Pink and Patti LuPone, who sang Evita’s Don’t Cry For Me Argentina as part of a tribute to Andrew Lloyd Webber.
Ed Sheeran, who could not attend the ceremony, won two prizes – best pop vocal performance for Shape Of You and best pop album for Divide.
There were also posthumous awards for Leonard Cohen and actress Carrie Fisher, who won best spoken word album for the audio version of her memoirs, The Princess Diarist.