This article focuses on frontline managers (FLM) who, until recently, have been neglected as key actors in the implementation of human resource management policies and subsequent employee performance outcomes. This research finds that FLMs are not a homogenous entity who act as robotic conformists, but rather evolve and become important agents shaping organisational performance outcomes and worker effort. The article extends social exchange theory to present a ‘zone of reciprocity’ that refines understanding of the causal chain between different FLM styles, HR policy and employee performance outcomes of organisational citizenship behaviour and commitment. The data are survey responses from 613 employees who all work and report to specific FLM in a single medical device multi-divisional organisation. The article offers new theory development as well as implications for practitioners interested in FLM and the HR performance causal chain.