Gen Outdoor replaces Kinetic in handling the business in the UK, while Media Keys picks up the business in other European markets.
Gen pitched in conjunction with Media Keys, and the two agencies will continue to work together on the business.
The managing partner of Gen, Michael Higgins, said: "This new force is a genuine alternative: an international network operating Gen's transparent business model, and is of particular interest to advertisers concerned about sharing media services with its competitors."
Higgins added that Gen is expecting to be "involved in several other major pitches in the forthcoming months".
Initiative and MindShare will continue to handle Samsung's UK media business and global account respectively.
Gen works on a fee basis, as opposed to the remuneration system that most outdoor specialists operate.
In March this year, the agency won 20th Century Fox's £4 million outdoor planning and buying business.