A sustainable, evidence-based intervention to motivate current blood donors to recruit new donors was evaluated using a quasi-experimental, in-service trial at three donation centers. Participating blood donors in three conditions (N = 734), received (1) an evidence-based leaflet designed to enhance recruitment motivation and five postcards facilitating recruitment and donor registration, (2) five postcards alone, or (3) no materials. Self-reported donor recruitment by donors was measured at 1-week and 6-week follow-up. At 1-week and at 6-week follow-up, donors in both intervention conditions reported talking to more people about donation and asking more people to donate than control participants. Intervention participants also reported persuading more people to register as a donor than control participants. Results indicated that postcards plus leaflet was somewhat more effective than the postcards alone. Donors intentions to recruit at 1-week follow-up mediated the behavioral effects at 6-week follow-up. Motivating and facilitating recruitment of new blood donors through existing donors has the potential to continually replenish the donor population.