Public service motivation (PSM) and ethical behavior are central concerns in public administration. Yet, experimental evidence on the causes of ethical behavior and the causal effects of PSM remains scarce, curtailing our understanding of both. This article draws on a novel survey experimental design to improve this understanding. The design is based on a simple insight: asking about PSM can render salient PSM-oriented identities of respondents. By randomizing the order of PSM and outcome questions, PSM may be exogenously activated among survey respondents, and the causal effects of this activation assessed. Drawing on this design and a sample of over 5,000 Chilean central government employees—the largest experimental PSM survey sample to date—we find that PSM activation enhances willingness to report ethical problems to management. This provides the first experimental evidence that PSM may promote ethical behavioral intent, and suggests that activating public employees’ PSM can benefit public sector ethics.