HWR, a division of Hilton International, has 36 resorts worldwide, with four more set to open in 2003.
Hilton reduced an agency shortlist of six to three for the work, with B-M beating a final shortlist of Weber Shandwick and Hill & Knowlton to secure the business.
B-M director Suzie Warner, who leads a five-strong team on the work, said the account was initially on a six-month project basis.
Warner said the PR campaign would target the travel trade press, before focusing on the consumer media.
She added that the campaign, which will kick off next week, would stress the 'unique geographical spread' of Hilton Worldwide Resorts.
HWR has hotels in the Americas, the Caribbean, the Arabian Gulf, Egypt, Europe, Israel, Asia-Pacific and on islands in the Indian Ocean.
B-M will aim to refine a 'consistent message' to create awareness of the HWR brand.
Hilton International director of product development Philippa Gould said: 'Hilton has always had a strong position in the corporate market, but we have been looking at our resorts business and think it's become difficult to ascertain what a resort is.
'With this new brand, we have created a set of brand standards. We have applied stringent criteria, one of which is that, for a hotel to be called a resort, it must be able to offer a self-contained holiday.
'Purchasing decisions in the resort sector are strongly influenced by recommendations and word-of-mouth, making PR an essential part of our comms strategy,' she said.
The first aim of the PR campaign will be to raise awareness of the HWR brand before the World Travel Market at ExCeL in London from 11 to 14 November.