This article explores the associations between self‐reported Public Service Motivation (PSM) and preferred job traits, study choice, and observable prosocial behaviour. We studied three subject pools covering over 250 university students in Germany. We used laboratory experiments with monetary rewards to measure altruism, fairness, strategic fairness, and cooperativeness, and a post‐experimental survey on subjects' PSM. Higher levels of PSM were not associated with studying public administration but were positively associated with altruism and negatively with strategic fairness. The experimental data reveal robust subject pool effects. After controlling for PSM, public administration students behaved more altruistically and displayed less merely strategic fairness than business students. And they behaved more cooperatively than business and law students. These behavioural findings about future bureaucrats corroborate cumulative earlier survey evidence about the higher prosocial tendencies of public sector employees. They point to the danger of crowding out such tendencies through overly extrinsic management tools.