Little is known about the factors that influence regulatory agencies' decision making. We posit that regulatory agencies are influenced by the firms they regulate, but not exclusively via political influence as is argued in the traditional regulatory-capture literatures. Instead, regulatory decisions are indirectly shaped via third-party actors whose signals reduce uncertainty in the agency's pursuit of legitimacy. Focusing empirically on the U.S. Department of Agriculture's approval of genetically modified organisms (GMOs), we find that signals from salient stakeholders and peer agencies have a positive influence on product approval and that their effects vary under different dimensions of uncertainty. We also discuss the implications of these findings for business-government relations and for nonmarket strategy.