Despite theoretical support suggesting a strong linkage between HR systems and knowledge management outcomes, only limited empirical evidence exists on the relative contribution of HR practices, particularly as experienced by individual employees, to facilitating intrafirm knowledge flows. Further, even fewer studies have investigated key intermediate mechanisms by which HR practices affect knowledge sharing attitudes and behaviour. Drawing on a survey of 135 core knowledge employees from three Irish-based firms, we found that reciprocal task interdependence, feedback from others, selective staffing and socialisation, relationship-oriented training and development, and line management support for knowledge sharing were the main factors associated positively with employee perceptions of a social climate that encourages cooperation and teamwork orientation. The implications of our findings are discussed.