Cochrane will join WBUK in April next year and will report to Josh Berger, president and managing director.
She will be responsible for marketing across all of WBUK’s operating divisions - WB Pictures International, Warner Home Video, WB International Television Distribution, WB Digital Distribution, WB Interactive Entertainment and WB Consumer Products. She will manage a team of 44 marketing staff and join the executive board.
Cochrane left Channel 4 last month as part of a restructure of the broadcaster's marketing operation. She had been at C4 for 10 years, and had overseen the development of its multi-platform products, including E4, More4, 4 Music and 4oD.
Josh Berger said: Polly is one of the most respected marketers of her generation with a proven track record of innovation and creativity that’s second to none.
"I’ve no doubt she will inspire our talented UK marketing group to even greater heights, and be a superb addition to WBUK’s senior management team.
Prior to Channel 4, Cochrane was head of advertising and promotions for Channel 5. She started her career at WCRS.