NatMags and Hearst, which publish consumer magazines both sides of the Atlantic, including Cosmopolitan, Best, Harper's Bazaar, Prima, Men's Health and Esquire, will use 5 Fifteen's browser-based software, Ad Depot.
Ad Depot will be adopted by 600 users across both companies companies (250 in the UK and 350 in the US) – the biggest single order that 5 Fifteen has ever received.
The system will be used across the publishers' titles to maximise ad revenues by leveraging an integrated advertising sales process. 5 Fifteen managing director Rod Fenwick said the contract was "for not less than five years".
Simon Horne, NatMags general manager, added: "Ad Depot will provide NatMags with an integrated approach to contact and lead management, proposal and order processing, across multiple media.
"It will also replace disparate legacy systems and provide anytime and anywhere access for sales staff to customer data, helping us to respond to our advertisers more efficiently."
Hearst Magazines is a subsidiary of the US-based Hearst Corporation and through its digital media unit it publishes internet and mobile sites for many top magazine brands, as well as non-magazine websites, such as Delish.com and TheDailyGreen.com.
In the UK, Hearst publishes 20 titles under its wholly owned NatMags subsidiary.
