This article examines the opportunities and challenges that private social standards pose for labor organizations. It explores different labor responses to private social standards in East African cut flower industries. The analysis incorporates the concept of labor agency in global value chain analysis and reveals how retailer-driven chains offer more room for labor organizations to exercise their agency than the traditional cut flower value chains. Labor organizations have been able to influence social standard setting and implementation, and to use standards to further labor representation at production sites. However, labor organizations' ability to seriously challenge the prevailing governance structure of the cut flower value chain appears extremely limited.