Apart from the Hammersmith Apollo, which was previously managed by Clear Channel, the sites were not previously represented.
Opportunities on offer will include bespoke media, experiential and pop-up installations.
The contract will initially run until September, covering the Olympics.
Ryan Horn, managing director of SEI Media, said: "SEI Media, as a proven innovative media business consultancy, is looking forward to working closely with Mama Group to deliver impactful and inspiring media, and experiential activation with great brands and clients this summer."
SEI Media recently worked with Manchester City Football Club and Gigapixel FanCam to create a 'Spot-the-Balotelli' campaign, which challenged fans to spot avatars of players such as Mario Balotelli and Sergio Aguero, in a picture of the crowd.
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