"There is no tongue and it is really not a big deal to kiss," the 42-year-old actress will tell syndicated TV entertainment show "Access Hollywood" in an interview set to air on Wednesday.
"I am not saying, 'Don't tune in to watch Jennifer on the show,' because she is fantastic and you get to see us together again," Cox says. "But if you think it is just about a major make-out session, you will be disappointed."
Cox and Aniston co-starred on the long-running NBC sitcom "Friends," which ended in 2004.
In the season finale of "Dirt," airing on March 27, Aniston, 38, guest stars as a lesbian magazine editor and rival to Cox's character, the ruthless tabloid queen Lucy Spiller.
"When she first arrived, everyone was really quiet," Cox says. "It was like they were giving her respect, and I was like, 'This is my bud, Jen. Come on people, let's have some fun.' And by day two, everyone was more loose, and by day three, we were having a ball."
Aniston has a "great sense of humor," Cox says. "That girl cuts up just as much as the rest of us. She is very fun and she's goofy, and she is just a doll."