This paper investigates One Health (OH) applied to antimicrobial resistance (AMR) to deepen and nuance its conceptual underpinnings and inform effective implementation. We consider how models of OH and AMR wedded to bioscience assumptions of life obscure biosocial complexity and reinforce the misleading assumption that scientific knowledge of AMR is generated outside social systems. With reference to in-depth interviews with medical practitioners, scientists and policy-makers working on AMR in Australia and the UK, we explore accounts of OH action on AMR. We show that the implementation of OH is subject to some fragmentation due to workforce organisation, funding arrangements and the absence of detailed guidance for translating OH into practice. Despite OH aspirations for transdisciplinary cooperation and innovation, human-centrism and somewhat incommensurable professional and scientific views on OH constrain trust in the policy approach and limit effective action. We discuss how, in some settings, OH action on AMR does resemble policy aspirations when emphasis is placed on collaborative humility, a finding that underlines OH’s biosocial character. We argue for the development of more robust biosocial models of OH to guide its application to AMR in real world settings.