This paper focuses on Hans Kelsen’s reflections on political parties. During the interwar period, Kelsen participated in a controversy over whether political parties were a necessary part of the democratic process. The debate forced Kelsen to produce a defence of political parties to emphasise their functionality and define their place in his particular definition of democracy. This contribution considers the following aspects. First, the reasons why Kelsen thought political parties are necessary for democratic life are explained. Second, the doctrinal oppositions against which he elaborated his defence of political parties are clarified. Third, the programme that Kelsen conceived of to enhance political parties in a constitutional democracy is examined. Finally, the contemporary questions that have arisen in relation to Kelsen's conception of political parties are scrutinised. Kelsen’s contribution to the debate about the role of political parties was intimately related to the presence of strong criticisms of that role. This makes his reflections even more interesting today, considering the present relative decline of the political role and appeal of parties.