Abdul, who rose to fame as a chart-topping singer in the late 1980s, alleged in a lawsuit filed in Los Angeles County Superior Court on Friday that Lythgoe sexually assaulted her in a lift during the early seasons of TV singing competition series American Idol.
Lythgoe, the producer of several hit television talent competitions, allegedly groped Abdul's breasts and genitals, among other unwanted physical contact in a hotel elevator after a day of auditions for Idol.
Abdul tried to push him away and ran as soon as the elevator doors opened, court documents said.
Reuters was not immediately able to reach Abdul or Lythgoe for comment.
Lythgoe denied the allegations, according to TMZ.
"For more than two decades, Paula and I have interacted as dear - and entirely platonic - friends and colleagues," he told TMZ.
"Yesterday, however, out of the blue, I learned of these claims in the press and I want to be clear: not only are they false, they are deeply offensive to me and to everything I stand for."
According to court documents, Abdul immediately reported the assault by Lythgoe, an Idol producer at the time, to her representatives but did not take action for fear of losing her job, the lawsuit said.
Moreover, Abdul's contracts prohibited her from speaking out, the lawsuit said.
Another alleged assault took place years later when Abdul worked as a judge on So You Think You Can Dance, according to court documents. The star, 61, enjoyed renewed popularity in the early 2000s starring as a judge on talent TV series.
The lawsuit alleges Lythgoe, 74, assaulted her on the couch of his Los Angeles home after a work dinner. Abdul again firmly rejected him and "immediately left Lythgoe's home," court documents said.
In the lawsuit, Abdul levels other allegations at the entertainment industry mogul, including that Lythgoe once called to taunt her and said it had been "seven years and the statute of limitations had run" on the alleged assaults.
The lawsuit alleged that the star also witnessed Lythgoe assault one of her assistants on So You Think You Can Dance.
The lawsuit was submitted days before the December 31 filing deadline established under the California's Sexual Abuse and Cover-Up Accountability Act.
The legislation allows individuals to bring certain sexual abuse lawsuits that would otherwise have fallen outside the statute of limitations.
