The agency defeated three others in a pitch late last month to net the account, believed to be worth a six-figure sum. The brief will cover corporate and consumer PR work for the firm's 200 stores across the UK and Ireland.
The firm has been without a PR agency for the past six months. Prior to that, work was handled by Colman Getty PR.
Waterstones marketing director Leslie Miles, to whom the agency reports, said the decision to hand the brief to HC was prompted by a desire to make use of the agency's nationwide network of offices and corporate communications capacity.
HC consumer director Alan Twigg, who heads the agency team, said the PR effort will look to enhance the Waterstones brand as well as providing grassroots support to 'build customer relationships'.