Zenith Media has swiped Hachette's UK partworks account from BBJ without a pitch, with the relationship possibly extending outside the UK.
The account, worth pounds 1 million last year, is set for new launches and will spend an estimated pounds 3 million this year, the majority on TV ads.
Hachette, which is owned by Renault parent Lagadere, is one of France's largest companies. It launched in the UK in 1998, and is set to increase its presence as it moves to compete against the likes of De Agnostini and Eaglemoss.
In January, Zenith Media, with creative by the production company X-pression, will launch two heavyweight TV campaigns worth pounds 2 million to advertise two new publications - a weekly partwork on how to interpret astrology and a fortnightly publication about motorbikes.
Tim Greatrex, the deputy managing director and new-business director of Zenith Media, said: 'We are delighted to have been appointed as Hachette's media partner and look forward to assisting it in meeting the huge challenges it has set itself.'
Tracey Stern will become account director on Hachette.