Randy Jackson, Mariah Carey, host Ryan Seacrest, Nicki Minaj and Keith Urban of American Idol.
The audience for American Idol slumped 19 per cent to 17.9 million viewers in the US, its lowest season opener, despite the debut of judges Mariah Carey, Nicki Minaj and Keith Urban, according to early ratings data released on Thursday.
The two-hour premiere of the show's 12th season on Fox television also lost 19 per cent of the 18-49 age group most coveted by advertisers, Nielsen figures showed. Total viewers dropped to 17.9 million from 21.9 million in 2012.
Despite the drop, American Idol was still the most watched show by a huge margin on US television on Wednesday night, beating all shows combined in the 18-49 demographic on the three other biggest TV networks.
Fox executives also noted that Idol beat the 2012 September premiere of NBC singing show rival The Voice by some 46 per cent in total viewers.
American Idol, long a ratings juggernaut for Fox, lost its eight-year crown as the most watched show on US television last year to Sunday Night Football.
Singers Carey, Minaj and country artist Keith Urban joined the show as judges after Jennifer Lopez and Aerosmith frontman Steven Tyler left last year.