Secret police are generally viewed as key institutions in autocrats’ repression apparatus. However, we lack clear empirical evidence on the link between secret police and repression. Instead, recent studies indicate that the surveillance provided by secret police reduces physical human rights abuses. This paper re-examines the relationship between secret police and physical state repression. We identify four mechanisms linking these variables, deterrence, targeting, organizational practices, and institutional self-preservation. These mechanisms provide contrasting expectations for the overall relationship but also contextual expectations on when secret police may (not) increase repression. To test these expectations, we collect data on the global existence of secret police. Results indicate that secret police are associated with increased physical repression, particularly when they must develop a reputation to deter dissidents or when multiple rival security organizations exist. In contrast, older, more established secret police or ones without institutional rivals are not associated with physical repression.