In addition to its 129 properties, the NTS owns 78,000 hectares of land, and cares for more than 400 islands and over 400 miles of footpath. The charity had never previously used a PR firm to work on the countryside portfolio.
The contract was awarded following a competitive pitch last month.
Angela Casey, managing director of Pagoda Porter Novelli, said: "This contract really plays to our skills and interests with the Munros, wildlife hotspots, gardens and reserves that make up part of the National Trust for Scotland’s portfolio. The organisation’s contribution to our understanding of Scotland’s natural beauty is worth promoting further."
Pagoda Porter Novelli was formed in April by the merger of Pagoda PR and CM Porter Novelli, creating one of Scotland's biggest agencies. It has a range of UK-wide clients including the Scotch Whisky Experience, the Portavadie resort in Argyll and Bute, and Heriot-Watt University.