Prior literature proposes two opposing hypotheses of how national regulations could influence CSR motivation. The mirror hypothesis suggests that corporations will be more motivated to invest in CSR if there are strong and well enforced national CSR-related regulations because such institutional settings pressure CSR not only by direct regulations but also with normative pressures important for an organization’s reputation and legitimacy. On the contrary, the substitute hypothesis proposes that there will be more CSR motivation in countries of lax CSR-related regulations because corporations would feel the need to fill the institutional void or to avoid stricter regulations in the future. We apply a multi-method design focusing on the micro-foundations of CSR motivation to further examine and resolve this contradiction. Specifically, we examine how institutional regulations affect individual-level CSR motivation and elaborate on the role of trust in regulating institutions as a crucial psychological variable in this process. We find that explicit CSR motivation is generally high in laxly regulated contexts but can be equally high in stringently regulated contexts if the trust in regulatory institutions is high. With our findings, we underline and clarify the strong role of regulatory institutions on CSR and the crucial role of trust in regulatory institutions in this process. We discuss theoretical and practical contributions for CSR management, the field of business and society, as well as international business.