It is believed M2M and John Ayling also bid for the planning business, which was previously handled in-house.
The win encompasses media planning across all traditional media, plus buying for all non-print media. Press buying will be managed by the company's in-house agency, Bourne Media. In 2005, Warner Breaks spent in the region of £3m on its media planning and buying.
Jane McIvor, Warner Breaks sales and marketing director, said: "We chose BLM Media because its team demonstrated a thorough understanding of our business challenges and audience, and an ability to drive better value and innovation for our business."