This paper analyzes the semantic aspect of the effect of populism in power on parliamentarism. The research focuses on the case of Serbia between 2001 and 2022, which corresponds to the post-Milošević era of contemporary Serbian political history and includes a decade before and after the populist Serbian Progressive Party (SNS) took power in 2012. Drawing on the traditions of conceptual history and rhetorical political analysis, this paper reconstructs the debate over the concept of parliamentarism in Serbian parliamentary debates during the period under observation in order to analyze how populist agents’ interpretation and use of the concept of parliamentarism related to and affected established conceptual conventions. The paper argues that the excessive centralization of power in the hands of the populist executive, which marked the first decade of SNS rule, was accompanied by SNS deputies’ attempt to redefine the concept of parliamentarism through the rhetorical reconstruction of its internal morphology. This attempt was manifested in SNS deputies’ contestation of the established conventions of articulating the concept of parliamentarism with the concepts of parliamentary sovereignty, which implied the superiority of parliament in the institutional system of the polity, and ministerial responsibility, understood as the effective scrutiny of the executive by the institution of parliament as a whole.