This thesis examines in detail the three major Vietnamese constitutional reforms of 1992, 2001, and 2013. In doing so, it examines the core purposes of constitutional changes related to the political legitimacy of the Party-State and investigates the factors that support or hinder the transition of the Vietnamese socialist constitution to liberal democratic constitutionalism. It does so by looking at Vietnamese history, culture, the circumstances of the emergence of each constitutional reform in the larger context of the crisis of the political legitimacy of the Party-State, the changes in the Vietnamese Communist Party’s policies, the procedure of drafting each constitution, and the aims and the substance of these changes. This study contributes to the ongoing discussion on constitutional transition in socialist regimes in two important ways. First, is represents the first comprehensive examination of all the major Vietnamese constitutional reforms. Second, it draws on not only international academic scholarship but importantly original Vietnamese sources, ranging from secondary literature of Vietnamese scholars, to original Party and State documents, particularly National Assembly deputies’ speeches, and Vietnamese media and blogs. The finding of the thesis is that there were three major factors that had a significant influence in the Vietnamese constitutional reforms of 1992, 2001 and 2013, namely, the Vietnamese Communist Party; state agencies and officials; and political and legal culture, such as village culture, Confucianism, colonialism, and socialism. The Party, state agencies and officials were the main factors that hindered these constitutional reforms, mainly because the Party-State introduced these reforms as a part of the ongoing negotiation with the people to retain the Party hegemony.