The $155m (£100m) deal will create a new DreamWorks Classics unit, with control of Classic Media’s roster of over 450 films and 6,100 episodes of TV shows, including Postman Pat, Noddy and Rocky & Bullwinkle.
Classic’s co-chief executives Eric Ellenbogen and John Engelman will run the new division.
DreamWorks’ chief executive Jeffrey Katzenberg said he would bring the new characters into many of the firm’s operations, including films, TV shows and theme parks.
Classic Media is currently owned by a subsidiary of US private equity firm GTCR. Based in New York, it owns 450 film titles and more than 6,100 episodes of animated and live-action programmes.
DreamWorks, which has seen its share price fall in recent years as DVD sales suffer, is the studio behind box office hits including Shrek and Madagascar.