Nilsen, 25, a plumber before becoming a professional singer, was crowned on Thursday world pop idol, following a special edition of the talent contest involving winners of the British and overseas programmes.
Nilsen, who sang Beautiful Day by Irish rock band U2 in front of a live studio audience in London, beat off the challenge of US Pop Idol Kelly Clarkson to take top spot.
Belgian Idol Peter Evrard was third in the contest that featured 11 singers. Britain's Will Young came fifth.
Although she did not place highly in the contest Jordanian singing sensation Diana Karzon gave a performance that left judges speechless – but most likely due to the language barrier.
Jordan's Diana Karzon left judges
After singing the Arabic love song Ansani Ma Binsak, the judges agreed it was difficult to comment on a song they did not understand.
"It wasn't spine tingling, but I enjoyed it, whatever it was," Canadian judge Zack Werner said.
The first Pop Idol show appeared in Britain in 2001, becoming an instant success. Similar series followed in 10 other countries - all designed to manufacture pop sensations.
Viewers from the competitors' countries voted to choose their world idol with Nilsen scoring maximum points in nine of the 11 polls.
"This is totally amazing," said a tearful Nilsen after being crowned champion. Turning to his fellow competitors, he said: "I love you guys."
Nilsen won the Norwegian version of Pop Idol last May - his subsequent single She's So High instantly topping the Norwegian chart.