The agency has held the Mauritius account since 2009 and successfully secured a further three-year contract after a ten-way pitch process.
It is expected to promote Mauritius via consumer marketing, public relations and travel trade with an aim to increase the number of UK visitors.
Jonathan Sloan, managing director at Hills Balfour, commented: "We know the product and understand what is required to drive incremental business. In a saturated market we need to cut through the noise, not simply to harvest returning visitors, but to create new visitors, above and beyond existing fans of Mauritius."
The firm has also been newly appointed to represent Tourisme Québec, also for a three-year contract.
The agency will be responsible for increasing awareness of Québec as a holiday destination and to boost both leisure and business tourism.
Sloan said: "We are thrilled to have been given the opportunity to represent Québec within the UK. It is a fascinating province with a wealth of culture and authentic experiences and I am delighted that we will be showcasing these to the UK media and trade."