This paper is an original empirical tentative to explain collective action outcome in the domain of food safety. We examine conditions and institutions that influence pesticide residues level in vegetables using econometric analysis on data gathered by 60 farmers organizations in Vietnam. Findings suggest that collective action affects safety by providing members with technical assistance, monitoring and certification. The expected increase of free-riding in larger groups is not an issue when members are properly supported and monitored. The contribution of public authorities and ecological conditions to safety remains controversial while market forces do not seem able to drive the production of safer vegetables.