Worker rights advocates seeking to improve labor conditions in global supply chains have engaged in private political strategies prompting transnational corporations (TNCs) to adopt codes of conduct and monitor their suppliers for compliance, but it is not clear whether organizational structures established by TNCs to protect their reputations can actually raise labor standards. We extend the literature on private politics and organizational self-regulation by identifying several conditions under which codes and monitoring are more likely to be associated with improvements in supply chain working conditions. We find that suppliers are more likely to improve when they face external compliance pressure in their domestic institutional environment, when their buyers take a cooperative approach to monitoring, and when their auditors are highly trained. We find, further, that a cooperative approach to monitoring enhances the impact of auditor training, and that auditor training has a greater impact on improvement when coupled with a cooperative approach than with external compliance pressures. These findings suggest key considerations that should inform the design and implementation of monitoring strategies aimed at improving conditions in global supply chains as well as theory and empirical research on the organizational outcomes of private political activism for social change.