Explaining how policies may be changed over time is a fundamental theme common to the study of public policy and governance. Scholars have developed several competing perspectives on how and why policy change occurs; while policy practitioners are largely focused on the successful negotiation and implementation of policy improvement and occasional major policy reforms. This chapter focuses on frameworks for explaining how policy agendas shift, how policy change occurs, and how some proposals for change are constrained. In the real world of complexity, wicked problems and mediatised debate, the authority and capacity of the state are subjected to many countervailing pressures. The explanation of policy change must take account not only of how Ministers are involved in setting priorities and mobilising political support, but also how public agencies manage the policy process – including their contributions to policy framing, policy design, engagement, evaluation, and managing conflicting views within civil society. In the governance era, policy change has become a complex and nuanced enterprise. This chapter reconsiders the utility of classic accounts of policy dynamics concerning evidence-based policy, ideology, and populist partisanship in addressing complex policy challenges.