This book introduces international bureaucracy as a key field of study for public administration and also rediscovers it as an essential ingredient in the study of international organisations. To what extent, how and why do international bureaucracies challenge and supplement the inherent Westphalian intergovernmental order based on territorial sovereignty? To what extent, how and why do international bureaucracies supplement the existing international intergovernmental order with a multi-dimensional international order subjugated by a compound set of decision-making dynamics? International bureaucracies constitute a distinct and increasingly important feature of public administration studies. However, the role of international bureaucracies has been largely neglected in most social science sub-disciplines. This book takes a first step into a third generation of international organisation (IO) studies. It will be of immense value to academics in politics and international relations as well as practitioners in public administration in domestic governments and international organizations.