Objectives To conduct a process and impact evaluation of Double Up Food Bucks (DUFB) Heartland, a nutrition incentive program, to facilitate program delivery and sustainability at farmers markets and grocery stores, and to examine the impact on Supplemental Nutrition Assistance Program (SNAP) customers. Methods Across 4 years, we employed a mixed methods approach, including surveys with customers (n = 678) and vendors (n = 223), and interviews with market managers (n = 52) and grocery store employees (n = 38). Study samples were obtained using a geographically-stratified, probability-proportional-to-size sampling plan. Customer surveys included demographic, social, dietary and health-related variables. Survey respondents included SNAP customers who had used DUFB (n = 382) and those who had not (n = 296). Results DUFB customers were primarily female (81%) and white (48%), with a mean age of 46 ± 15 years. Non-DUFB users had similar characteristics. Of DUFB users, 56% indicated food insecurity issues and 27% rated their general health as fair to poor. Most learned of DUFB on-site. DUFB customers reported being able to afford more produce (98%), consuming a greater variety of produce (59%), and reducing their intake of unhealthy foods (45%). Importantly, 93% of DUFB users indicated the presence of the program influenced their decision to shop at the site. Among non-DUFB users, most were unaware of the program but 98% indicated they were likely to participate next time they shopped. Grocery store cashiers reported DUFB implementation was easy and it did not add time to complete a sales transaction. Store directors felt DUFB brought about a greater focus on locally grown produce and all expressed a desire to continue the program. Market managers stated participation in DUFB increased produce sales, and the number and diversity of customers. Market vendors viewed DUFB as beneficial, stating it resulted in a new customer base and increased produce sales. Conclusions Results were instrumental in identifying successes and challenges faced by locations that were implementing the DUFB program. DUFB was well accepted with few implementation barriers noted. However, many SNAP users were not aware of the nutrition incentive program. Findings will be used to refine materials and develop strategies to extend program reach. Funding Sources USDA Food Insecurity Nutrition Incentive Program.