Retail farmers' markets are seen as key institutions in a more "civic agriculture," but little is known about how they promote small business entrepreneurship. Drawing on research in economic sociology and economic geography, this paper examines the role of social learning in vendor innovation. Data from a 1999 mail survey of farmers' market vendors in California, New York and Iowa show that business innovation, as represented by intensity of vendors' successful enterprise expansion, was modest. Social learning through engagement with customers contributed to more innovative marketing by vendors, while social learning thought engagement with customers and fellow vendors increased the likelihood of vendors diversifying to additional markets beyond the farmers' market. Certain individual and enterprise characteristics also influenced vendor innovation. This suggests that, although important, the beneficial effects of social learning for vendors at farmers' markets remain moderated by human capital and structural factors.