This paper aims to discuss international migration in terms of the methodology of public administration discipline. Thus, it seeks to gain insight of recent challenges the public administration has faced by utilizing international migration as a global policy issue. Public administration, which has witnessed debates on its object of inquiry, came across new epistemological challenges as public policy issues have become more complicated than ever. This fact forces scholars to consider its scope, unit of analysis, and object of inquiry in that it has faced unprecedented blurring of lines between political and administrative realms. In addition to that, increasing interdependency and interactions across borders have posed challenges against classical notion of the nation state and public administration, including advices for revisiting their previous definitions and constructions as to how we recognize them. International migration constitutes the new policy challenges that public administration has to deal with. This paper argues that public administration should function as Science of the State and respond to contemporary challenges with interdisciplinary methods. To this end, first it sets descriptive elements of international migration. Then, it discusses them in terms of the scope, unit of analysis and research methodology of public administration.