"I kept saying no! I mean, what crazy nut is gonna go out there in a bikini at almost 40 years of age against a girl who is 20 and probably cosmetically enhanced?" said DioGuardi in April's Women's Health, Us Weeklyreported Monday.
DioGuardi donned the bikini at the end of a finale performance with eighth-season hopeful Katrina Darell -- who received the nickname "Bikini Girl" due to her attire when she initially auditioned.
Since it was the end of her first season on American Idol's judging panel, DioGuardi called her decision to wear the bikini a "defining moment."
"Like, 'She's serious and industry, but also as kooky as everyone else on this panel,'" DioGuardi told Women's Health. "I looked a little pasty. But hey, at least I didn't wet myself!"
DioGuardi recently appeared Maxim's March issue and said she's able to stay in shape by hitting the gym four times a week.
"Boxing, treadmill, step-ups, walking lunges, sprints... I mix it up," she told Women's Health. "And weight training is important as you get older. You build muscle, which burns fat when you're at rest."