Modern jurisprudence regards constituent power as the radical truth of modern democracy. The purpose of the study is to explore in systematized form the existing relation between both concepts of constituent power and democracy, bearing in mind the ideas of collective acts of self-regulation, popular sovereignty and their legitimation. The thesis of the author is that democracy and constituent power are interchangeably linked. Democracy outlines conditions regarding the execution of the constituent power in a way to achieve democratic openness, while constituent power is a juristic expression of the democratic impulse, a mechanism that can be used if necessary, to modify the democratic government by changing the Constitution. The study proposes a legal interpretation of the interaction between the democracy and constituent power, by concluding that the latter lays the foundations of the legal order, it is an expression of the will of the sovereign, therefore it can be understood as a radical truth of modern democracy. Despite there are a lot of publications in Bulgaria analyzing in depth the concepts of constituent power and democracy, there are no significant legal studies exploring the relation between both concepts. Despite democracy and constituent power are concepts vastly examined by the political science and sociology, the current paper limits its scope on the legal aspects of the interaction between them.