The contract gives Viacom Outdoor the right to sell all of its outdoor formats across the Tyne & Wear Metro's 57-station network.
The Metro is focused around Newcastle, Sunderland and Gateshead and is second in size only to the London Underground.
Viacom Outdoor estimates that the contract is worth £10 million over five years and gives the company a 27 per cent share of all UK rail journeys.
As well as handling advertising on the London Underground, Viacom Outdoor also holds the rail contracts for Arriva Trains Wales, Chiltern, Merseyrail, TransPennine Express, Central Trains, Scotrail, First Great Western Link and GNER.
Separately, Viacom Outdoor has hired Emap Advertising's marketing director, Sue Todd, to take on the same role within the company. She replaces Mike Baker, who has taken on a European role at Viacom Outdoor.
The appointment reunites Todd with Tim Bleakley, who left Emap last October to become a joint managing director at Viacom Outdoor.