Numerous national parks have been established worldwide to protect nature, but this has not been without social consequences for neighbouring communities. Since the social and economic vitality of adjacent communities is being recognized more and more as indispensable for the success of conservation objectives, the quality of park-community relations has become a critical issue. A four-year investigation into the social impacts engendered by two national parks situated in the Saguenay region of Quebec (Canada) was conducted, according to a social impact assessment method. Several impacts and changes were identified on resource management, on the local economy, on the tourist industry, on involvement and participation of local actors and on the social organization of the neighbouring communities. The significance of these impacts varied according to the community and the actors involved. The results of the present research point to the determining role of the government in general, and of the park management in particular, in the process of local community development. In this regard, recommendations are addressed to local communities to improve their partnership with national parks.