The deal with , which oversees sales for Turner Broadcasting's entertainment channels in the UK, applies to the , Cartoon Network Too, Boomerang, Cartoonito and Turner Classic Movies.
Turner will still retain control of selling integrated multimedia advertising campaigns to clients, while Platform-A will sell online display ads to the mass market.
Turner Broadcasting's websites are popular with children, who visit the websites to play online games. The company said that its Cartoon Network website currently averages 23.5m page impressions and 753,000 unique visitors per month.
The deal comes after AOL expanded Platform-A to Europe last month, in a move that combines the internet company's existing advertising operations in Europe, including the AOL UK sales team, Advertising.com, ADTECH, and Buy.at.
The expansion also integrates AOL's technologies, including contextual search by Quigo, behavioural targeting by TACODA and mobile ad-serving by Third Screen Media.
Brendan Condon has been named head of Platform-A's international operations.
Simon Cox, the vice-president of TMI, said: "This is a good deal for all parties. We will still work on an a la carte basis with our key clients developing bespoke packages, which combine both traditional and new-media. AOL will focus on mass market growth."
Michael Steckler, the managing director of Platform-A UK, added: "This agreement delivers on the promise of Platform-A, which is to provide publishers access to the most advanced tools and solutions to generate more ad revenue from their inventory.
"We're pleased to have the opportunity to work with a great media company like TMI."