Rheumatoid arthritis (RA) is a chronic, inflammatory condition which may cause pain, stiffness and fatigue. People who have RA have reduced levels of physical activity due to these symptoms. Interventions targeting physical activity behaviour in this population have had limited efficacy. This paper describes a protocol for a pilot randomised controlled trial (RCT) of a theory-based intervention delivered in a community setting designed to promote physical activity in people who have RA. The aim of the pilot study is to assess the impact of the intervention on moderate-intensity physical activity in people with RA. The objectives are to obtain reliable estimates regarding recruitment rates; participant retention, protocol adherence and generate potential effect size estimates to inform sample size calculations for a main trial on physical activity participation. Semi-structured interviews will be conducted with a selected sample of participants to explore their experiences. Participants will be recruited from direct referrals from the rheumatology clinics in a public hospital. Participants meeting inclusion criteria will be randomised into a 6week physical activity intervention (four sessions delivered over a 6-week period by a trained physiotherapist) or a control group (physical activity information leaflet). Results of the pilot study will provide data to determine if a larger RCT is feasible. Qualitative data will inform intervention design and delivery. The findings will be disseminated to health professionals, in peer-reviewed journals and conference presentations.