Understanding how Public Service Motivation (PSM) is tied to ethical or unethical conduct is critically important, given that civil servants and other public-sector employees throughout the world have been shown to exhibit high PSM levels. However, empirical evidence about the relationship between PSM and ethical or unethical behavior remains limited, due in part to the challenges of observing unethical conduct and overcoming social desirability bias in self-reported measures. We address these challenges by employing incentivized experimental games to study the relationships between PSM and two types of unethical behavior—corruption and dishonesty—as well as one type of ethical behavior: altruism. Based on data from approximately 1,870 university students at three research sites in Russia and Ukraine, we find evidence of a robust negative association between PSM and willingness to engage in corruption and a positive association between PSM and altruistic behavior. Results concerning dishonesty are more mixed. Our findings indicate that corruption and dishonesty are related yet fundamentally distinct concepts, particularly with respect to their compatibility with PSM. The findings additionally demonstrate that hypotheses about PSM and behavioral ethics generated in the Western context generalize well to the starkly different institutional context of the former Soviet Union.