Abstract The process of any democratic government relies heavily on constitutionalism and the rule of law. The past and present governments in Nigeria did very little in observing the rule of law in dealing with its citizens. The past democratic governments especially the Obasanjo government 1999 – 2007 subverted the rule of law and violated so many aspects of our constitution with impunity. However, the Yar’adua government came in 2007 and the government saw constitutionalism and the rule of law as cardinal principles and so observed and respected it to a Certain degree. However, this does not mean that his government had never violated the rule of law but in comparison with other government, his administration fared better. This study attempts a critical analysis of constitutionalism and the rule of law under President Yar’adua. Adopting a qualitative research method with reliance on the secondary sources of data, it discovered that the regime had strong adherence to the rule of law which is a key requirement for democracy to thrive. It further observed that the regime operated within the confines of constitutionalism which imposes limitations on the process of government, a development which manifested in the strict adherence to the rule of law and the protection of human rights by that regime. The study recommended good governance, press freedom, free and fair elections, judicial independence among others as the panacea to the success of constitutionalism and the rule of law in the country. Keywords: Constitutionalism, Rule of law, Constitution, Democracy..