Experience Corps® (EC) was designed to simultaneously increase cognitive, social, and physical activity through high-intensity volunteerism in elementary school classrooms. It is, therefore, highly likely that EC participation may alter pre-existing patterns of lifestyle activity. This study examined the impact of "real-world" volunteer engagement on the frequency of participation in various lifestyle activities over a 2-year period. Specifically, we examined intervention-related changes on reported activity levels at 12 and 24 months post-baseline using Intention-to-Treat (ITT) and Complier Average Causal Effect (CACE) analyses, which account for the amount of program exposure. ITT analyses indicated that, compared to the control group, EC participants reported modest increases (approximately half a day/month) in overall activity level, especially in intellectual and physical activities 12 months post-baseline. Increases in activity were not found at the 24-month assessment. CACE models revealed similar findings for overall activity as well as for intellectual and physical activities at 12 months. Additionally, CACE findings suggested modest increases in social activity at 12 months and in intellectual and passive activities at 24 months post-baseline. This community-based, health promotion intervention has the potential to impact lifestyle activity, which may lead to long-term increases in activity and to other positive cognitive, physical, and psychosocial health outcomes.