Using panel data from the US states, we document a robust negative relationship between state-level government corruption and ideological polarization. This finding is sustained when state polarization is instrumented using lagged state neighbor ideology. We argue that polarization increases the expected costs of engaging in corruption, especially deterring marginal low-level corruption. Consistent with this thesis federal prosecutorial effort falls and case quality increases with polarization. Tangible anti-corruption measures including the stringency of state ethics’ laws and independent commissions for redistricting are also associated with increased state polarization.