U.S. rap star Eminem opened the show with a performance of his new song Walk on Water, with Skylar Grey standing in for Beyonce to sing the other part in the duet.
Rita Ora hosted and performed, opening the show alongside Kurupt FM, the stars of BBC comedy "People Just Do Nothing", with a skit that featured London Mayor Sadiq Khan.
Mendes performed There's Nothing Holdin' Me Back, the victor of Best Song. Winners are selected by fans across the continent.
Louis Tomlinson, from the boy band One Direction, landed the best United Kingdom and Ireland act.
Coldplay was named best rock act, while the best-alternative prize went to Thirty Seconds to Mars.
"U2's impact on music, pop culture and social issues around the world has been tremendous", said Bruce Gillmer, producer of the awards ceremony. U2, recipients of the global icon award on the night, performed "Get Out of Your Own Way" from Trafalgar Square.
British R&B singer Rita Ora performed the hosting duties, as well as a mashup of her 2017 hit Your Song, alongside her new single Anywhere.
The cable channel also runs the Video Music Awards which are renowned for top performances and the occasional controversy, including pop diva Lady Gaga wearing a dress made of meat to the ceremony in 2010.
The Detroit rapper also took the award for Best Hip Hop, an honour which he appeared to find slightly baffling.