Lythgoe tweeted Saturday he found out about being fired shortly after he returned to the United States from a vacation, The Hollywood Reporter said.
"Just had 10 days in the Bahamas, rain everyday. I get back to the States and get fired. Sad!," Lythgoe tweeted.
However, Lythgoe said he retained his job on Fox's "So You Think You Can Dance."
"Yes, don't worry. I'm on #SYTYCD. Fox still loves me," Lythgoe said. "It's not a personal thing they just feel IDOL needs new leadership after 12 Seasons."
While some people have blamed Lythgoe for poor choices of theme nights on "American Idol," former Idol competitor Jacob Lusk showed support for the show's former executive producer.
"You are one the best things that's ever happened to TV," Lusk tweeted.
Fox confirmed Lythgoe's firing, and that of fellow executive producer Ken Warwick, in a statement.
"The passion and dedication that Nigel Lythgoe and Ken Warwick brought to American Idol guided the show to become a true cultural phenomenon," the statement said. "While we are saddened they will no longer be executive producers on the show, we are grateful for their tremendous contributions and look forward to continuing to work with them on additional projects."