This study explores the impact of timebanking, where individuals earn time credits, nonmonetary currency, on promoting volunteerism among older adults. This study employed a quasi-experimental design with 116 timebank group (TBG) participants and 114 comparison group (CG) participants from 2021 to 2022. TBG received time credits to exchange for rewards, while CG received no time credits (i.e., volunteering as usual). The intervention of timebanking lasted for 1 year. Volunteering behaviors were tracked via an app, and intentions to volunteer were assessed at baseline (T0), after 6 months (the midpoint of the intervention, T1), and after 12 months (the endpoint of the intervention, T2). The use of rewards by TBG participants was also recorded (e.g., for personal use or sharing with others). Furthermore, focus group interviews were conducted to understand how rewards influenced participants' volunteerism. TBG had significantly higher weekly volunteer hours at T2 (β = 1.37, p = .021) and increased intent to volunteer at T1 (β = 0.54, p = .001) and T2 (β = 0.51, p = .001) compared with CG. Participants using rewards personally volunteered more at T2 (β = 2.09, p = .014), although sharing rewards with family and friends or donating rewards to others did not yield the same effect. The qualitative study suggested that a sense of feeling recognized generated by timebanking may encourage increased volunteering and that personal reward use enriched the volunteer experience, and individuals sharing rewards with family and friends experienced a sense of fulfillment and reinforcement of their prosociality. Timebanking effectively encourages late-life volunteering. The study provides practical implications for promoting volunteering among older people.