The 41-year-old 'Charlie Angels' star began dating Madden, 35, after being introduced by Nicole Richie, a close friend of the actress and wife of Benji's twin brother, reported Showbizspy.
"Benji is madly in love with Cameron, but she wants to take it slow - he isn't her usual type. He has dated a lot of Nicole's friends in the past but Nicole really wants this one to work," a source said.
Madden and Diaz apparently have been spending a lot of time at her Hollywood home, and have also been spotted working out together at an Equinox gym in Los Angeles.