The rumours have been circulating town since they began working on their new film, The Break Up.
Vaughn, 35, insists that he and Aniston, who has recently split with Brad Pitt, are only friends. He spoke with a reporter at the British premier of his film Wedding Crashers, where he said, "We’re making a film together, man. Jennifer’s a sweet girl but she’s very vulnerable right now and has been through a really hard time."