Institutions have always been of great concern to public administration, in both a practical and an analytical sense. The new institutionalism, developing in different versions from the early 1980s, has contributed new and varied insights on how institutional factors shape the life of public administrations. Instead of mainly focusing on formal rules and organizations, as in traditional (“old”) institutionalism, new institutionalism perceives of institutions in a broader sense, as patterned behavior also following from informal rules, norms, and habits. Different institutional perspectives continue to develop with some mutual borrowing of ideas, but they also specialize, which help us understand how public administrations are shaped by the historical legacies of institutions, institutional rules and norms that socialize organization members; institutions as incentive structures designed to increase trust and compliance; organizational adaption to major institutional trends, and institutions as cultures of communication. These perspectives are specific lenses that bring valuable, complementary insights, particularly when it comes to their varied conceptualizations of agency: strategic calculation, social adaption and imitation as well as social construction in communicative settings. However, it is argued that institutionalism has largely neglected political aspects in the interaction between institution and agency, which needs to be explored and elaborated on in future empirical research and theoretical development. The political character of public administrations is very complex and varies from individual preference falsification in order to adapt to institutions, to subversive actions for trying to undermine or to secure existing institutions when important values are at stake in public administrations.