The pitch, handled by The Haystack Group, involved a final shoot-out between DDB and WCRS, with Lowe being knocked out at an earlier stage.
The incumbent, FCB London, declined to repitch for the business.
Weetabix wants DDB to provide a new brand direction for the whole Weetabix cereal portfolio, including Weetabix, Weetabix Minis, Alpen, Ready Brek and Weetos. The move is part of a wider-ranging review of the company's activities, instigated by its newly arrived chief executive, Ken Wood.
Weetabix is currently experiencing buoyant sales. Last year's £70 million in sales kept Kellogg's Cornflakes off the top position.