The enactment of the revised Payment Services Directive (PSD2) by the European Union, has pushed banks to develop digital open banking platforms to enhance market competition and promote innovation in the banking industry. PSD2 mandates banks to offer APIs to provide access to banking data to external third-party providers (TPPs). This mandate might disrupt the role of banks since external complementors such as fintechs have the legal right to access and leverage banking data to offer innovative banking services. As such, the emergence of regulated open banking platforms engenders complex interdependent relationships between banks and fintechs. Drawing on a case of an open banking platform by Nordea Bank, we aim to examine these interdependencies with emphasis on the engagement between banks and external complementors in a regulated platform context. We conclude with insights into the lack of access control by platform owners and new conditions of platform openness. © 2023 International Conference on Information Systems, ICIS 2023: "Rising like a Phoenix: Emerging from the Pandemic and Reshaping Hu. All Rights Reserved.