Mendes also won the Biggest Fans award earlier in the evening, and is still up for Best Artist - against Ariana Grande, Ed Sheeran, Kendrick Lamar, Miley Cyrus and Taylor Swift. The night's big victor, Mendes, sung his best song-winning track "There's Nothing Holding Me Back" from a huge light box.
Eminem, who opened the show by unveiling his new single "Walk on Water" - ahead of the release on Friday of his latest album "Revival" - won for best hip hop artist. He then emerged onstage in jeans and a black hoodie to perform the slow-burning number live, with Skylar Gray filling in on the duet duties Beyoncé performed on the recording. The rapper picked up the best hip hop gong.
The 24-year-old singer took to the stage to perform his song "Strip That Down" at the annual award show on Sunday night (November 12) held at The SSE Arena, Wembley in London, England.
Grime star Stormzy brought the hometown vibes, arriving in a police auto and performing "Big for Your Boots".
The best video, claimed by U.S. rapper Kendrick Lamar, was one of the few awards to be chosen by the MTV team.
Fuming Lukaku turned on Man Utd teammates after Chelsea blank
Lukaku netted in the 55th minute but Lozano turned the game on its head, scoring a minute later before putting Mexico ahead on 60 minutes.
Coldplay was named best rock act, while the best-alternative prize went to Thirty Seconds to Mars. "Congratulations to all the winners and thank you to the incredible crowd!"
Apart from the occasional hint of marijuana smoke wafting across the arena, there were few of the unscripted-feeling moments that made past shows stick in the memory.
U2 performed in London's Trafalgar Square the night before the MTV awards, along with DJ Guetta, to a crowd of 7,000 who won free tickets in a ballot.
Mendes, 19, who launched his career by posting song covers to the internet before getting signed to a record label, also scooped the "biggest fans" award.
U2 were crowned the Global Icon, with Bono singing a burst of Stormzy's "Blinded By Your Grace" as they collected the trophy.