Usher: Voted Best R&B Act and Best Album
But Craig David, who scored a hat-trick of gongs last year, only won one prize at the ceremony where most of the winners are voted for by music fans.
Usher, who has had hits with You Make Me Wanna and Pop Ya Colla, walked off with two of the biggest awards - Best R&B Act and Best Album.
So Solid Crew were named Best Newcomers and Best UK Garage Act after recently hitting number one in the UK with single 21 Seconds.
Click here to watch a clip of So Solid Crew perform 21 Seconds on Top of the Pops
Oxide and Neutrino, who perform as a duo but are also members of So Solid Crew, took the collective's tally to three awards when they were named recipients of the Best Video trophy.
Missy 'Misdemeanour' Elliott was voted the Best Hip-Hop Act, while Shaggy, who has had two UK number one singles in the last six months, was named Best Reggae Act.
The awards - which were first held in 1996 - were handed out at the London Arena, and R Kelly, Samantha Mumba and Mis-Teeq were among the performers.
But Luther Vandross, who had been due to perform and pick up a Lifetime Achievement award, was absent after deciding not to fly following the 11 September attacks.
Craig David was also absent, choosing to remain in America after performing at New York's John Lennon tribute concert.
In other categories, Dr Dre was named best producer and Destiny's Child were given the Best Single award for Independent Women Part One.
Producer and performer R Kelly was honoured for his outstanding contribution to the genre.
He performed the ceremony's finale, paying tribute to victims of the 11 September attacks.
Outkast, who had most nominations, lost out in all four categories they were named in.
Usher - full name Usher Raymond - was awarded for his third album, 8701, which went to number one in the UK in July 2001.
The singer, 22, from Atlanta, Georgia, shot to fame in 1997 with his album My Way and has already had two Grammy nominations and won three Billboard Music Awards.
Click here to watch a clip of Usher sing U Remind Me on Top of the Pops
So Solid Crew were the first performers of the night and confirmed their place as the most successful new urban UK act to hit the charts since last year's awards were held.
Hailing from south London, they have risen from the underground club and carnival scene to be chart-toppers seemingly overnight.
One of their members, Ashley Walters, 19, was remanded on conditional bail charged with making threats to kill in August.
'Significant'
Mobos director Kanya King recently told BBC News Online that the awards have become a national event and an important barometer for the UK music scene.
"It's become one of the most significant dates in the music industry calendar and the biggest champion for urban music in the UK," she said.
The ceremony was hosted by American singer Kelis and BBC Radio 1 DJ Trevor Nelson.
Nominees for the awards were chosen by a panel of experts but winners of 15 of the 18 categories were voted for by fans.