The 36-year old former England centre-half is struggling for game time under Alan Pardew at St James’ Park and is entertaining a loan move to Glasgow for the remainder of the season.
Despite Pardew saying Campbell would remain in a Magpies shirt, the ex-Arsenal and Tottenham star is eyeing a shift to Parkhead to help Lennon’s side in their title pursuit.
"I'd look at the situation, I'd look at everything. But Celtic have to come to me and Newcastle have to come to me and say x, y, z. Newcastle would have to decide what they want to do,” he said.
"I couldn't come to an agreement with Celtic last summer, that's the way it goes at times. I was still impressed by the club.
"Sometimes six months down the road people can wake up and realise things better, look at the bigger picture.
"We'll see what happens. Watch this space, eh?"