This paper presents an analysis of GlobalGAP adoption by small-scale fruit and vegetable farmers in Thailand focusing on GlobalGAP group certification, the costs and perceived benefits of GlobalGAP adoption, and the factors influencing standard adoption. GlobalGAP is the most important private standard for producers in the Thai horticultural sector concerning access to high-value markets, especially to Europe. We find that support by donors, exporters and public-private partnerships is vital to enable small-scale farmers to adopt the standard. GlobalGAP group certification encourages the formation of new institutional arrangements between farmers, exporters and donors. In our sample only participants from a development program were successful in adopting GlobalGAP and within the program farmers were either organized in certification groups where the Quality Management System (QMS) was run by farmers themselves, by an exporter or by a donor. The results of the adoption analysis suggest that household characteristics (age, education, wealth, availability of family labor), farm characteristics (farm size, intensity of irrigation use), the number of agricultural trainings subjects attended, prior involvement in high-value supply chains, as well as exporter and donor support in terms of costs of compliance, technical advice and management of the QMS influence GlobalGAP adoption.