
Eyeconomy will sell all advertising on DailyExpress.co.uk, DailyStar.co.uk, OK.co.uk, New-magazine.co.uk and Star-magazine.co.uk.
Sales had previously been handled in-house by the Richard Desmond-headed group.
Eyeconomy will also handle banner ad sales and look for sponsors across the various sites.
Farzad Jamal, group internet controller of Express Newspapers, said the decision to appoint Eyeconomy was due to it being a well-established agency.
He adds: With its expertise and impressive relationships with advertisers and agencies, we are confident it is the best agency to deliver our required revenue goals.
Eyeconomy is part of parent company Media Corporation and its clients include AOL, Dell, American Express and I-Level.