PurposeFlexible work arrangements (FWAs) are routinely offered in organizational policy, yet employee access to FWAs is highly dependent upon support from their immediate supervisor. There is little empirical research that specifically investigates the role of the human resource function (HR) in supporting managers to implement FWA policy. Through the lens of HR systems theory, the purpose of this paper is to examine how HR supports managers to implement FWAs.Design/methodology/approachUsing a case study in the Australian Insurance industry, this paper analyzes corporate documents and interviews with 47 managers, supervisors and HR staff across four diverse business units.FindingsThis study identifies supervisors’ perceived ability to implement FWAs as a potential barrier to utilization. Five mechanisms of HR support to overcome perceived barriers are identified in the data. An HR system that enables managers to support FWAs requires alignment of HR policies; the provision of supportive technology; an HR structure that facilitates proactive advice and support; HR business partners with influence; and managerial training on FWAs.Practical implicationsThis paper provides HR practitioners with insights into the mechanisms that can support managers to implement FWAs or other devolved HR policies.Originality/valueApplying HR systems theory, this case study utilizes the perspectives of senior managers, supervisors and HR staff to explain how the HR function supports or constrains managers in the effective implementation of FWAs.