About 6000 fans crammed the Sydney Opera House forecourt on Sunday to watch the finale of the Network Ten TV talent show, which was held entirely in the open air for the first time.

Performers and fans ignored the rain for the two-hour show.

Carr, 26, who had been the favourite throughout the series, looked ecstatic when he was declared the winner.

He thanked a long list of people from security staff to make-up artists and his girlfriend. He also heaped praise on his good mate and rival Dickens.

"Thank you, I'm shaking," he said.

"And to this man, Luke, he is the most amazing man.

"... I'm the godfather of his child."

Dickens, 25, a shearer from Young in country New South Wales congratulated Carr.

"This here is the man and that is why he is here," he said.

Carr wins a recording deal with Sony, a car and $200,000 towards developing his craft.

He'll also record his winner's single, You.

A spectacular fireworks display lit up the sky, and extra star power came from performances by artists including Kasey Chambers and Shane Nicholson and the Pot Bellies.

Former Idol runner-up Jessica Mauboy thrilled the crowd by performing her new single from her recently released album Been Waiting, and dancers from Ten's So You Think You Can Dance opened the show.

All top 12 contestants from this year's Idol returned to the stage and judges Kyle Sandilands, Marcia Hines and Ian Dickson wished them all well.

Tonight was the first time two males have contested the final round since the very first Australian Idol in 2003.

AAP