The agency has held the business, which consists of the IPA, Abbot Ale and Wexford Irish Cream Ale alcohol brands, for five years.
The move comes as a fresh blow to McCann, which is still reeling from a spate of client discontent. Somerfield recently left for M&C Saatchi, and Coca-Cola last month handed the ad account for its main brand to Mother.
Unilever is reviewing its £60 million Birds Eye business.
News of the Greene King review comes only a week after Rupert Howell, McCann's UK and Ireland chairman and president, EMEA, appointed Robert Campbell as the agency's creative head and Robin Price as its chief operating officer.
The agency is considered to have produced some of its best work for Greene King during the past two years. Its most recent campaign for IPA led with a spot in which a man survives experiences that should have killed him because Death is in the pub having another pint of the ale.
No-one at McCann-Erickson was available for comment as Campaign went to press.
- Newsmaker, p18.