While many social theories and concepts have been used within the sustainable tourism literature to identify key elements, stakeholders, and relationships that are central to sustainable tourism development and the tourism-community relationship, there has been limited use of the social capital concept for examining the sociocultural dimension of sustainability, despite its growing appeal within the social sciences as an analytical tool. Based on ethnographic case study research within the mountain resort community of Steamboat Springs, Colorado, this paper adopts social capital as a heuristic device for examining tourism development s sociocultural sustainability. It explains the foundations of the social capital concept with networks, norms, and resources as key components, and the existence of bonding, bridging, and linking social capital. Findings suggest that mountain resort tourism has affected such social capital outcomes and sociocultural sustainability indicators as quality of life, community participation, and the associated notions of democracy, equity, and empowerment, in both positive and negative ways, leading to a spirit of community cooperation, friendliness, grass-roots initiatives and community action group development running alongside social exclusion, transience, and political powerlessness. These findings give empirical weight to using social capital as a guiding construct for the qualitative examination of socioculturally sustainable tourism.