O'Leary was hosting the ITV1 reality series when Cowell and Minogue's relationship is reported to have taken place behind the scenes.
Watch Dermot O'Leary talking about The X Factor below:
When asked whether he accidentally walked in on Minogue and Cowell, O'Leary laughed: "No! Thankfully. I was uncorrupted when it came to that."
The presenter also revealed that he is hoping to put his infamous X Factor opening sequence dance routines "to bed".
"Like all these things they put it to a focus group and for some God forsaken reason the focus group seem to like it," he told Digital Spy. "So, you may see it occasionally, put it that way."
O'Leary also downplayed reports of rivalry between The X Factor and The Voice, commenting: "[The Voice] is a strong show and you've got two good singing shows on the TV. It's not the end of the world."