Von Anhalt, who is married to Zsa Zsa Gabor, filed the defamation suit seeking at least $10 million in damages Wednesday.
The claim stems from comments O'Reilly made during a Feb. 22 segment of "The O'Reilly Factor."
"Look, this guy's a fraud," O'Reilly said, according to a transcript of the show posted on the network's Web site. "We know he's a fraud. But let's -- what I want to talk about is -- he's done. His credibility is -- is finished."
Last month, von Anhalt filed legal documents seeking a DNA test to determine if he is the father of Smith's baby girl, Dannielynn. He has said he carried on a decade-long affair with the former Playboy centerfold.
Since the show aired, von Anhalt said people give him dirty looks when he goes to the grocery store.
"They say, 'Look, here comes the fraud,"' he said. "I get lots of e-mails from people bad-mouthing me. It's very embarrassing."
FOX News spokeswoman Dana Klinghoffer said Thursday that FOX had not received the suit yet and could not comment on it.
Smith's former boyfriend Larry Birkhead and her most recent companion, Howard K. Stern, whose name appears on the baby's birth certificate, also claim to be the baby's father.