The vocal quartet were the first-ever recipient of the award, which recognises the massive impact the operatic group has had in the classical genre, selling more than 25 million albums worldwide.
Speaking at the ceremony the band's Urs Buhler said: "It's really strange to me, our success - the four of us are singers, we've all been singers for a long time prior to Il Divo, we go into the studio, we take songs, we record them the way that we all feel them and out comes Il Divo, and that's it!"
Composer John Barry was also honoured posthumously with the Outstanding Contribution to Music award for his work including for numerous film scores, including the themes to 'Born Free', 'Out of Africa' and James Bond films including 'Diamonds are Forever'.
John, who passed away in January, aged 77, had his award presented by 'Born Free' star Virginia McKenna to lyricist and long term collaborator Don Black.
At the end of the evening Dame Shirley Bassey delighted the audience with a stunning performance of one of John's most recognisable hits, 'Goldfinger', another James Bond song, which she originally sung for the film's soundtrack.
Violinist Tasmin Little won Critics' Award while Trumpeter Alison Balsom picked up Female Artist of the Year.
British conductor and music director of the Royal Opera House Antonio Pappano was named Male Artist of the Year and Arvo Part Composer of the Year.
Norwegian violinist Vilde Frang was chosen by a panel of classical critics for the Newcomer Award while Classic FM Album of the Year was picked up by Andre Rieu and Johann Strauss Orchestra for 'Moonlight Serenade'.
The Classic BRIT awards 2011 will be broadcast on the UK's ITV1 on May 29.
Full list of winners of the Classic BRIT Awards 2011
Newcomer Award in association with MasterCard: Vilde Frang
Female Artist of the Year - Alison Balsom - 'Italian Concertos'
Composer of the Year -Arvo Part 'Symphony No. 4'
Male Artist of the Year - Antonio Pappano 'Rossini: Stabat Mater'/'Verismo Arias'
Critics' Award - Tasmin Little 'Elgar: Violin Concerto'
Artist of the Decade - Il Divo
Classic FM Album of the Year - Andre Rieu and Johann Strauss Orchestra 'Moonlight Serenade'
Outstanding Contribution to Music - John Barry OBE