Introduction Sport is being promoted to raise population levels of physical activity for health. National sport participation policy focuses on complex community provision tailored to diverse local users. Few quality research studies exist that examine the role of community sport interventions in raising physical activity levels and no research to date has examined the costs and cost-effectiveness of such provision. This study is a protocol for the design, outcome, process and economic evaluation of a complex community sport intervention to increase levels of physical activity, the Health and Sport Engagement (HASE) project part of the national Get Healthy Get Active programme led by Sport England.

Methods and analysis The HASE study is a collaborative partnership between local community sport deliverers and sport and public health researchers. It involves designing, delivering and evaluating community sport interventions. The aim is to engage previously inactive people in sustained sporting activity for 1×30 min a week and to examine associated health and well-being outcomes. The study uses mixed methods. Outcomes (physical activity, health, well-being costs to individuals) will be measured by a series of self-report questionnaires and attendance data and evaluated using interrupted time series analysis controlling for a range of sociodemographic factors. Resource use will be identified and measured using diaries, interviews and records and presented alongside effectiveness data as incremental cost-effectiveness ratios and cost-effectiveness acceptability curves. A longitudinal process evaluation (focus groups, structured observations, in-depth interview methods) will examine the efficacy of the project for achieving its aim using the principles of thematic analysis.

Ethics and dissemination The results of this study will be disseminated through peer-reviewed publications, academic conference presentations, Sport England and national public health organisation policy conferences, and practice-based case studies. Ethical approval was obtained through Brunel University London's research ethics committee (reference number RE33—12).