The integrity of public officials is considered a key determinant of public trust in government and a central concept in good governance. An integrity system consists of all components, such as policies, practices, institutions and integrity guardians meant to contribute to the integrity of the organization at the heart of the integrity system. In this article we propose a theoretical model for the effectiveness of integrity systems that can be tested empirically. Six conditions are proposed as important for delivering the outcome of high integrity performance. Different configurations are expected to deliver the same outcome, because of varying developmental trajectories. Implications for further research are discussed. Points for practitioners Many countries have in place measures for dealing with corruption and unethical behaviour on the part of public officials. Rarely are these measures considered as part of a whole system. At the same time, there is little research evidence for the effectiveness of individual measures or the system as a whole. This article addresses these issues and is, therefore, important for policy makers who are developing anti-corruption measures.