The 36-year-old old actor was accompanied to the afterparty of his new movie 'The Hangover Part II' by the 'Tron: Legacy' star and onlookers at Monday's (23.05.11) bash at New York's Boom Boom Room said they were "definitely" together.
One insider told Life & Style: "Olivia was Bradley's date. He was always taking her hand or putting his hand on her lower back, it was really sweet. He took care of her all night.
"They were definitely together. At one point, they even wanted some alone time and hiked up the stairs to the roof, but they had trouble getting there!
"They left together at 12.15. They seemed really comfortable together."
Over the weekend, Bradley and Olivia - who was recently romantically linked with Justin Timberlake following her split from husband Tao Ruspoli - were spotted "flirting" at the 'Saturday Night Live' after-party, where they were joined by the 'SexyBack' hitmaker and actress Mila Kunis.
An onlooker told the New York Post newspaper: "It looked like Olivia was friendly with Justin, but flirting with Bradley."