Mendes -- who recently became the first artist under age 20 to score three No. 1 songs on Billboard's Adult Contemporary chart -- also performed "There's Nothing Holdin' Me Back" at the show, which took place in the British capital for the first time since 1996.
In line with MTV's decision to scrap male and female categories for its Movie and VMA shows earlier this year, this was the first EMAs without gender-specific awards.
Alongside Mendes, other big winners at the event included Eminem, who kicked off the show with the live premiere of his new single "Walk On Water," accompanied by a string orchestra and the song's co-writer, Skylar Grey, seated at a piano and more than ably filling in for <a href="/music/Beyonce">Beyoncé</a>.
The rapper was subsequently crowned best hip-hop artist, collecting his award from <a href="/music/Prophets-of-Rage">Prophets of Rage</a> members Chuck D, B-Real and Tom Morello.
"I want to thank the fans, and I want to thank MTV. But I also want to thank Chuck D and B-Real for so much inspiration. They're one of the reasons that I'm even able to be here right now. These guys are like gods to me," said Eminem, noting his own surprise at beating <a href="/music/Kendrick-Lamar">Kendrick Lamar</a>, <a href="/music/Post-Malone">Post Malone</a> and <a href="/music/Drake">Drake</a> for the best hip-hop award, given that he hasn't put out an album since 2013. "I got one coming though," he added.
Later in the show, <a href="/music/Camila-Cabello">Camila Cabello</a>, who is currently topping the U.K. singles chart and No. 2 in the Billboard Hot 100 with "Havana" featuring <a href="/music/Young-Thug">Young Thug</a>, continued her successful year, taking home the title of best pop. The Cuban-born singer also delivered one of the show's more colorful performances, leading dozens of dancers through a heavily stylized "Havana" complete with a striking swimming pool set design.
Ed Sheeran, who co-hosted the EMAs in 2015, accepted the award for best live via video speech -- as did Kendrick Lamar, winning best video for "HUMBLE."
Taylor Swift -- who led the nominations, but was not present in London -- failed to win in any of her six categories.
British singer <a href="/music/Rita-Ora">Rita Ora</a> proved an entertaining host, beginning the show with a pre-filmed skit that saw her running through London's streets in a dressing gown as she made her way to the venue, passing the city's mayor, Sadiq Khan, along the way. Later, Ora performed a carnival-esque medley of "Your Song" and "Anywhere," and carried out the traditional EMA hosting duties of elaborate costume changes, lame skits and gushing platitudes to everyone in attendance.
Other standout performances on the night included: <a href="/music/Travis-Scott">Travis Scott</a> flying high above the crowd on a mechanical eagle for "Butterfly Effect"; <a href="/music/The-Killers">The Killers</a>' Brandon Flowers hitting the high notes during an imperious "The Man"; British grime star <a href="/music/Stormzy">Stormzy</a> delivering a fiery "Big For Your Boots" from atop a mock British police car; and <a href="/music/Liam-Payne">Liam Payne</a> with a crowd-pleasing rendition of "Strip That Down."
As to be expected following this year's Manchester arena bombing and October's Las Vegas shooting, security was higher than ever at MTV's showcase European event, with an increased police and security presence visible all around the SSE Wembley Arena. They were, nevertheless, unable to prevent what appeared to be a planned stage invasion when a male member of the crowd successfully clambered onstage for around 30 seconds and unfurled a banner during <a href="/music/French-Montana">French Montana</a>'s rendition of "Unforgettable" before being escorted away.
Aside from some misfiring comedy routines, it was the only real hiccup in an otherwise slick and highly polished two-hour show that also saw <a href="/music/Clean-Bandit">Clean Bandit</a> deliver an enjoyable medley of "I Miss You," "Symphony" and "Rockabye," accompanied by guest vocalists Julia Michaels, Zara Larsson and Anne-Marie. Meanwhile, <a href="/music/Kesha">Kesha</a> delivered one of the EMAs more powerful moments with a stirring run through her empowerment anthem "Learn to Let Go."
<a href="/music/U2">U2</a>, who performed a free gig to 7,000 people at London's Trafalgar Square the night before, were also on hand to collect the previously announced global icon award from <a href="/music/Thirty-Seconds-to-Mars">Thirty Seconds to Mars</a> singer Jared Leto, who hailed the Irish band as "a way of life."
"Their songs are prayers. Their concerts [are] a church. They challenge us. They inspire us. They remind us that every moment in our lives in an opportunity to rise above and be part of the possibilities of life rather than its problems," Leto eulogized.
Collecting the global icon award, U2 guitarist The Edge joked, "People always ask: How have you kept your band together? It's four incredibly strong individuals [all with] strong wills. But there has to be a boss. There has to be one leader. One guy who calls the shots. Does the heavy lifting and comes up with all the ideas," he stated before delivering the punch line: "But I could not have done it without these guys' support. Truly, they are the wind beneath my wings."
Bassist Adam Clayton also spoke to the crowd, 90 percent of whom were not alive when U2 first got together, and dedicated the global icon award to Island Records founder Chris Blackwell. In one of the night's more unexpected moments, Bono passed up the opportunity to make a speech and instead sang a verse of Stormzy's "Blinded By Your Grace" by way of acceptance.
The show culminated in suitably celebratory style with <a href="/music/David-Guetta">David Guetta</a> performing his new single "Dirty, Sexy, Money" alongside French Montana and <a href="/music/charli-xcx">Charli XCX</a>.
MTV EMAs 2017 COMPLETE WINNERS LIST
Global Icon: U2
Best Song: Shawn Mendes, "There's Nothing Holdin' Me Back"
Best Artist: Shawn Mendes
Best Look: Zayn
Best New: Dua Lipa
Best Pop: Camila Cabello
Best Video: Kendrick Lamar, "HUMBLE."
Best Live: Ed Sheeran
Best Electronic: David Guetta
Best Rock: Coldplay
Best Hip-Hop: Eminem
Best Alternative: Thirty Seconds to Mars
Biggest Fans: Shawn Mendes
Best Push: Hailee Steinfeld
Best World Stage: The Chainsmokers, Live From Isle of MTV Malta 2017
Power of Music: Rita Ora
Lil' Kleine (The Netherlands)
C. Tangana (Spain)
Stormzy (U.K. and Ireland)
FULL PERFORMANCE LIST
Eminem, "Walk on Water"
Liam Payne, "Strip That Down"
Camila Cabello, "Havana"
Demi Lovato, "Sorry Not Sorry" / "Tell Me You Love Me"
Stormzy, "Big For Your Boots"
Rita Ora, "Your Song" / "Anywhere"
Shawn Mendes, "There's Nothing Holdin' Me Back"
Clean Bandit, "Miss You" ft. Julia Michaels / "Symphony" ft. Zara Larsson / "Rockabye" ft. Anne-Marie
U2, "Get Out Of Your Own Way" (pre-recorded at London's Trafalgar Square)
French Montana, "Unforgettable"
Travis Scott, "Butterfly Effect"
The Killers, "The Man"
Kesha, "Learn to Let Go"
David Guetta ft. Charli XCX, French Montana and Afrojack, "Dirty Sexy Money"