The first episode of this year's X Factor was watched by an average of 10.5 million people on ITV1, according to initial overnight figures.
The talent show's eighth series is the first without judge Simon Cowell, who is developing a US version of the show.
Take That's Gary Barlow, pop singer Kelly Rowland and Tulisa Contostavlos of N-Dubz have joined the panel.
Last year's opening episode achieved overnight figures of 11.1 million, the highest in the show's history.
On Saturday, viewers saw hopefuls including Janet Devlin from Northern Ireland, who won over the judges with her version of Elton John's Your Song, the cheeky 18-year-old Frankie Cocozza and the outrageous Tai Chi instructor Goldie Cheung.
ITV1's audience peaked at 12 million, the broadcaster said. On BBC One at the same time, The National Lottery: Secret Fortune was seen by an average of 3.5 million, followed by Casualty with 4.2 million.
Former Boyzone manager Louis Walsh is the only X Factor judge to remain from last year's panel.
Cheryl Cole quit to become a judge on the US version before being forced out of that role, reportedly because executives were afraid that viewers would not be able to understand her Newcastle accent.
And Dannii Minogue left, saying the show clashed with her commitments as a judge on Australia's Got Talent.
ITV has said Cowell would continue to be "an enormous presence backstage" and there has been speculation that he will return to the panel later in the series.
Critics have yet to be convinced by the new line-up.
Writing in the Sunday Mirror, TV reviewer Kevin O'Sullivan said Barlow was "a revelation", having "slipped into the Mr Nasty head honcho role with surprising ease".
He wrote that the new judges "weren't bad", but added: "Nor were they that great. Just average."
He wrote: "When Cowell's on board it's event TV... when he's not, it feels like non-event TV."
In The Observer, Morwenna Ferrier said Tulisa was "promising" as Cheryl Cole's replacement.
But she added: "Gary Barlow's attempts at brooding super-villainry often translate as po-faced."