O'Reilly wrapped up the allegations this January in a quick 15 days from when the lawsuit was drafted.
In response to a New York Times story published Saturday, 21st Century Fox says it knew of the settlement but not the monetary amount.
In a statement, parent company 21st Century Fox said was aware of the settlement, but not the sum, when it signed a $25m-a-year contract renewal.
Even so, 21st Century Fox reportedly began contract negotiations with O'Reilly, Fox News' most lucrative host, and agreed to a four-year, extended contract paying him $25 million a year.
It was already shocking when Fox News chose to dump its top-rated host Bill O'Reilly, after mounting revelations of sexual harassment and multi-million dollar settlements, earlier this year.
Fox News did not immediately respond to TPM's request for comment.
The company also said the contract included "protections. specifically aimed at harassment, including that Mr. O'Reilly could be dismissed if the company was made aware of other allegations or if additional relevant information was obtained in a company investigation".
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Carlson, who's gone on to pen an upcoming book on sexual harassment, condemned companies for settling claims or building arbitration clauses into an employee's contract in case a legal issue arose.
As other accusations swirled around FNC before, during and since, O'Reilly was finally canned after it was revealed that over $10 million had been paid out to settle other sexual harassment claims against him.
Ms. Wiehl agreed to destroy all communications between her and Mr. O'Reilly and eventually signed an affidavit dated January 17 retracting the allegations and promising not to sue, the report said.
Wiehl accused O'Reilly of harassment and "a nonconsensual sexual relationship", according to the Times, which cited unnamed sources briefed on the settlement.
The settlement involving Ms. Wiehl is the largest of at least six agreements reached between Mr. O'Reilly's accusers with either Fox News or its former employer.
Roger Ailes, the co-founder and former chairman of Fox News, was similarly ousted from the network in July 2016 amid a flurry of sexual harassment allegations dating back decades. When Wiehl first appeared on the show in 2001, O'Reilly said he had gotten her the job and that she owed him for it, to which she replied, "No, no, no". O'Reilly was sacked in April over initial reports of his settlements with five women over similar allegations.