This paper discusses the various ways that deliberative democratic theory intervenes in debates about constitutional theory. After a brief introduction, Section II begins with foundational views that employ deliberation as a framework to reconstruct constitutionalism as such. In Section III I canvas theories that delineating how we ought to be deliberating about constitutions within established liberal democratic orders. This moves the discussion from a constituent function of deliberation to a constituted function and role. This section pays special attention to public reason arguments. The question of how we should be deliberating about constitutional essentials naturally leads to the question of who should be deliberating about constitutional essentials in Section IV. There are three natural answers to this question: courts, legislatures, and citizens. Within deliberative democracy theory the answer is often a combination of these three but there are important variations. In Section V, I take a deeper dive into citizen participation in deliberative constitutionalism. I argue that deliberative constitutionalism offers a view of democratic constitutionalism that differs from political and popular constitutionalism both of which are focused on reducing the power of courts vis-à-vis legislative institutions rather than enhancing the participatory power of citizens.