This paper attempts to present the constitutional and legal frameworks for the constitutional oversight of the legislative oversight in Portugal and South Africa and the various mechanisms that enable the Constitutional Court to monitor legislative oversight. The paper also presents the most critical repercussions that resulted from applying the constitutional oversight system over legislative oversight and the impact of these repercussions on rights and freedoms. It also addresses the quality and integrity of legislation and the effects of this oversight on the relationship between the constitutional judiciary and the parliament. The study uses two basic approaches: the comparative approach to compare South Africa and Portugal and the analytical approach to determine the repercussions of constitutional oversight on legislative oversight. The study seeks to answer several research questions that help clarify the mechanisms necessary to exercise this oversight.