The agency has resigned the account after a series of disagreements over money, having produced just one campaign for the brand.
Grey picked up the business in February this year following a pitch against JWT, Joshua G2 and Doner Cardwell Hawkins. CHI & Partners, the incumbent on the account, refused to pitch for the business.
888.com, which is owned by 888 Holdings, is now in the process of approaching agencies and putting together a longlist for a pitch that is expected to start in August.
CHI won the account in October 2007 after the deregulation of gambling advertising. The Gambling Act 2005, which was introduced on 1 September 2007, allowed broadcast gambling ads to run in the UK. Alongside this legislation, the gambling industry also imposed a voluntary advertising code, which introduced a 9pm watershed on TV ads.
CHI's most famous work for the brand, which launched in February 2008, featured the comedian Vic Reeves dressed up as an 888 lady for the company's sub-brand, 888ladies.com.
888.com, which was founded in 1996, operates in 176 countries. The FTSE 250-listed company, which is headquartered in Gibraltar and also operates Casino-on-Net and Pacific Poker, announced last month that it would roll out additional games, outside of its online poker offerings.