The Amazing Race contestant, who is believed to be taking part in the new series of Australian Celebrity Apprentice, was rumoured to be seeing Cox shortly after she won the modelling reality show last year. However, he has now insisted that they are "just good friends".
Joliffe told the Herald Sun: "I haven't seen her for a while actually - she's been so crazy busy. Every time I speak to her she's like, 'I'm flying here', or 'I'm doing that'. It's unreal. I'm stoked for her."
Cox has also previously denied the romance rumours, saying: "We just went out as friends and then there was a story saying we were in love."
He also talked about his split from former Neighbours actress Erin McNaught in 2011, saying: "We ended nicely - no one did anything wrong, no one cheated, no one did this, no one did that, we just separated... growing apart."
Other than Joliffe, stars such as David Hasselhoff, Fiona O'Laughlin, Lauryn Eagle, Patti Newton and Marion Grasby are rumoured to have signed up for Celebrity Apprentice 2012.
Filming for the Channel Nine series is believed to get underway today (January 16) in Sydney.
> Erin McNaught, Nathan Joliffe deny cheating rumours
> Erin McNaught still "really close" to ex-boyfriend Nathan Joliffe