The agency will now produce all digital advertising campaigns for the film and TV production company, with particular focus on home entertainment releases.
In addition, the agency will work on one-off projects. The first is a brand campaign to support the launch of a new format on the Sony PSP that allows consumers to watch films via the games console.
Sony Pictures has used various agencies for digital campaigns in the past, including the regional digital shop Hyperlaunch New Media. In March, it launched a viral produced by Spinnaker to promote its Quentin Tarantino-backed horror film, Hostel. The viral can be seen at youhavebeenwarned.co.uk.
The appointment of Greenroom signals the company's intention to give digital advertising a strategic role in its marketing plan.
Jon Hamm, the Greenroom managing director, said: "The scope of the brief, with a focus on strategic and brand development as well as product-based campaign activities, makes this account extremely exciting for Greenroom."
Philip Dowgierd, the agency's head of strategy, added: "It's a brilliant brief. Content creators understand the new media landscape, but want to add traditional brand strategy to their online marketing techniques."