Neo-institutional theory has become a major approach to the social sciences generally, and this chapter will assess the utility of institutionalism for understanding public policy. This task is complicated by the various different strands of institutionalism–normative, rational choice, historical and discursive— each having different strengths and weaknesses in explaining policy choices. That said, there are some common strengths, such as linking structures to choice. There are also some common weaknesses, notably difficulties in explaining change. This chapter will focus on the capacity of institutional approach taken as a whole to address fundamental issues of policy formation, maintenance and change.