After winning song of the year for "That's What I Like", Mars won the record of the year Grammy for "24K Magic".
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.
"I remember seeing it firsthand - people dancing that had never met each other from two sides of the globe, dancing with each other, toasting with each other, celebrating together", he said.
Mars has won 11 Grammys in his career.
Kendrick Lamar was the night's second biggest victor, picking up five Grammys, starting with his first of the night for Best Music Video for "Humble", which also won Best Rap Song and Best Rap Performance. - Best pop duo/group performance: "Feel It Still", Portugal.
Then it was time for STING to present SONG OF THE YEAR, won by BRUNO MARS and THE STEREOTYPES for "That's What I Like", a category KENDRICK LAMAR wasn't nominated for, so he's still on tap for seven.
He ended his speech with a huge nod to JAY-Z - "Jay for president!" He joined Kendrick Lamar, Bono and the Edge for the broadcast's opening number. And after a rundown of everyone the music industry lost in the a year ago, ending with Linkin Park's Chester Bennington, Logic, Cara and Khalid perform 1-800-273-8255. Singer Janelle Monae introduced Kesha and tied the appearance to the current flood of women speaking up about sexual misconduct.
"We wanted to come together and honour the memory of the handsome, music-loving souls so cruelly taken from us", added Morris.
The Grammys also featured a tribute to music fans killed in attacks in Las Vegas and Manchester past year with country stars Eric Church, Maren Morris and Brothers Osbourne together performing Eric Clapton's mournful "Tears in Heaven".
Alessia Cara won the Grammy for best new artist, and remembered the time when she would "win" Grammys in her dreams while singing in the shower. - Best pop vocal album: "Divide", Ed Sheeran. And to those who would dare try to silence us, we offer you two words: "Time's up", Monae said in a reference to the Time's Up movement spreading from Hollywood to the music business.
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.