According to Nielsen figures on Friday, Candice Glover's victory over Kree Harrison was watched by 14.3 million viewers.
That's a 33% drop from the year before, when 21.5 million viewers saw Phillip Phillips claim the Idol crown. That represented the show's previous record low finale audience.
"American Idol" saw an even steeper 44 percent drop among advertiser-coveted young adults for Thursday's finale.
The lack of interest in the winner of this year's contest parallels the show's declining ratings for the season.
Fox is scrambling to revive the singing contest that once dominated TV, revamping the judges' panel and making yet-to-be detailed format changes.
Original judge Randy Jackson has already announced his exit.