Social trust is a crucial ingredient for successful collective action. What causes social trust to develop, however, remains poorly understood. The quality of political institutions has been proposed as a candidate driver and has been shown to correlate with social trust. We show that this relationship is causal. We begin by documenting a positive correlation between quality of institutions, measured by embezzlement, and social trust using survey data. We then take the investigation to the laboratory: We first exogenously expose subjects to different levels of institutional quality in an environment mimicking public administration embezzlement. We then measure social trust among the participants using a trust game. Coherent with our survey evidence, individuals exposed to low institutional quality trust significantly less.