The digital transformation era calls for digital innovations affecting the public sector, but such organizations often focus more on the efficiency and exploitation of current resources, ascribing less attention to explorative innovation. Innovation in new capabilities and technologies often require inter-organizational collaboration. In this context, public sector organizations do not operate in isolation—often engaging in interactions within their service sectors. While the contemporary literature on organizational ambidexterity primarily focuses on the balancing opportunities of a focal organization, radical sector-level development requires collaboration among various actors to achieve collective ambidexterity. Drawing on the research question of the influence of inter-organizational collaboration on the outcomes of digital initiatives, this exploratory case study on the Finnish water sector found that simultaneously operating modes of inter-organizational collaboration can facilitate different aspects of collective ambidexterity in an inter-organizational field and, consequently, the expected benefits from initiatives. Our theoretical contribution lies in demonstrating collaboration modes that can enhance specific aspects of collective ambidexterity. Accordingly, we suggest that collective ambidexterity through deliberately adopted modes of inter-organizational collaboration requires field-level facilitation in parallel with organizational ambidexterity. Furthermore, consequent practical implications for managing such collaborations are suggested for policymakers, interest groups, and the public sector.