This study uses a practices-resources-uses-performance linkage approach to examine the impact of High Performance Work Systems (HPWS) on firm performance in Professional Service Firms (PSFs). Based on data collected from 120 Irish accounting firms, findings suggest that firms with more HPWS have higher level of resources, i.e. human, social and organisational capital. These resources, in turn, create value for the firms when they are effectively utilised. Therefore, this study provides a comprehensive picture of how HPWS work in professional service firms by providing the conceptual and empirical support for the practices-resources-uses-performance value creation chain. These findings will help firms find mechanisms to improve their performance.