Background: There is an urgent need to increase population levels of physical activity, particularly amongst those who are socio-economically disadvantaged. Multiple factors influence physical activity behaviour but the generalisability of current evidence to such ‘hard-to-reach’ population subgroups is limited by difficulties in recruiting them into studies. Also, rigorous qualitative studies of lay perceptions and perceptions of community leaders about public health efforts to increase physical activity are sparse. We sought to explore, within a socio-economically disadvantaged community, residents’ and community leaders’ perceptions of physical activity (PA) interventions and issues regarding their implementation, in order to improve understanding of needs, expectations, and social/environmental factors relevant to future interventions. Methods: Within an ongoing regeneration project (Connswater Community Greenway), in a socio-economically disadvantaged community in Belfast, we collaborated with a Community Development Agency to purposively sample leaders from public- and voluntary-sector community groups and residents. Individual semi-structured interviews were conducted with 12 leaders. Residents (n = 113), of both genders and a range of ages (14 to 86 years) participated in focus groups (n = 14) in local facilities. Interviews and focus groups were recorded, transcribed verbatim and analysed using a thematic framework. Results: Three main themes were identified: awareness of PA interventions; factors contributing to intervention effectiveness; and barriers to participation in PA interventions. Participants reported awareness only of interventions in which they were involved directly, highlighting a need for better communications, both inter- and intra-sectoral, and with residents. Meaningful engagement of residents in planning/organisation, tailoring to local context, supporting volunteers, providing relevant resources and an ‘exit strategy’ were perceived as important factors related to intervention effectiveness. Negative attitudes such as apathy, disappointing experiences, information with no perceived personal relevance and limited access to facilities were barriers to people participating in interventions. Conclusions: These findings illustrate the complexity of influences on a community’s participation in PA interventions and support a social-ecological approach to promoting PA. They highlight the need for cross-sector working, effective information exchange, involving residents in bottom-up planning and providing adequate financial and social support. An in-depth understanding of a target population’s perspectives is of key importance in translating PA behaviour change theories into practice.