Regular physical activity is associated with a diverse range of physical and mental health outcomes, with the effects being particularly pronounced among older adults. Despite these health benefits, involvement in physical activity has been found to decline over the course of adulthood with older adults in particular risk of inactivity. A growing body of evidence, however, suggests that group-based settings that are sensitive to both the age-composition and gender-composition of their constituent members may represent an opportune means of supporting the improved adoption and maintenance of older adults in physical activity programs. The overall purpose of this feasibility trial is to test the effectiveness of a group-based physical activity program for older adults that is sensitive to both age-congruent and gender-congruent contextual factors, in supporting their sustained involvement in physical activity.