Oversight is one of the key functions of the National Assembly meant at identifying and avoiding inefficiency and waste, determination of government effectiveness and compliance with legislative intent. It is also a veritable tool for the fight against corruption and a constitutional tool for the realization of accountability of the government to the people. This study evaluates the role of National Assembly Oversight Functions on Corruption in the Federal Public Service and it is an attempt at documenting the significance of this political institution in addressing the most challenging issue of Nigeria's nascent democracy. By means of descriptive approach, case study and analysis of documentary sources and conversational interviews, a review of selected literature on the subject and the data analyzed revealed that the National Assembly have not been able to sanction those found wanting as regards to corruption in the Federal Public Service, and in addition, corruption and personal agenda of the Legislators hindered effective oversight functions of the National Assembly within the period under review. Therefore, the study recommended that access to required information to establish corruption should be broadened and stakeholders be allowed to feature in all legislative processes.