She and the 'Django' star raised eyebrows after they were spotted dancing together at an event in the East Hamptons in August 2013.
The couple has been spotted looking cosy with each other on several occasions last year. Sources say the 36-year-old actress and the 47-year-old actor are quietly dating but it's nothing serious yet.
According to People Magazine, Katie, who recently moved into a new Los Angeles home with her eight-year-old daughter Suri, has been seen visiting Jamie's nearby house 'often' where 'they spend hours together' each occasion.
A source tells the mag, "This is not some intense romance. Jamie and Katie are friends and have been for a long time. They are two adults who are attractive and single, and so apparently conclusions will be drawn.vBut contrary to those conclusions, they're not about to run off and make some serious commitment.”
The actress has known Jamie for years and even socialized together with her then-husband Cruise at a football game in 2006.
She and Jamie raised eyebrows after they were spotted dancing together at an event in the East Hamptons in August 2013.
That same summer, Jamie brushed aside talk of a romance and was quoted by ibtimes.com as saying: "In fact, it’s quite hilarious because we simply danced at a charity event along with a lot of other people."
Katie has remained single since she divorced 'Mission Impossible' actor, Tom Cruise in 2012.