Over the past three decades the Professional Service Firm (PSF) sector has emerged as one of the most rapidly growing, profitable, and significant in the global economy. In 2013 the accountancy, management consulting, legal, and architectural sectors alone generated revenues of US$ 1.6 trillion and employed 14 million people. PSFs play an important role in developing human capital, creating innovative business services, reshaping government institutions, establishing and interpreting the rules of financial markets, and setting legal, accounting and other professional standards. The study of PSFs can offer insights into the contemporary challenges facing organizations within the knowledge economy, and deepen understanding of more conventional organizations. Despite their significance, however, PSFs have until recently remained very much in the shadows of organizational and management research. The Oxford Handbook of Professional Service Firms marks the coming of age of PSF scholarship with a comprehensive and integrative exploration of current research and thinking on PSFs, featuring contributions from internationally renowned scholars in the fields of organizational and management studies. It is divided into three distinct sections – the professions, the firms, and the professionals that work within them – and covers subjects from governance and leadership to regulation, entrepreneurship, and diversity. Bringing together a broad range of empirical and theoretical perspectives, the Handbook offers many potentially important insights into the contemporary challenges of organizations in the knowledge economy and suggests new lines of inquiry that may shed further light on the activities and performance of PSFs and the professionals who work within them.