In the interplay between realism and idealism in the realm of politics, Islamic political jurisprudence, as an Islamic legal-political system, can pave the way for growth and advancement while simultaneously enabling individuals to enjoy the world's blessings. Concurrently, in disciplines such as law, politics, and jurisprudence, a concept known as 'custom' or 'usage' plays a significant role in all social interactions worldwide. In post-1979 Islamic Iran, jurisprudence has taken the lead in addressing socio-political issues. Therefore, it is crucial to examine how custom in political jurisprudence intertwines human idealism with empirical realities. This article, employing a descriptive-analytical method and relying on library research, concludes that custom endeavors to ground the jurisprudence of the metaphysical realm and integrate it with societal realities in the political sphere. Consequently, custom serves as the intersection of political jurisprudence and political science. This article delineates the most important instances of recourse to custom in politics and determines its boundaries. By addressing the question of whether political jurisprudence is idealistic or realistic and which ideals can be compromised in socio-political life, the conclusion is reached that political jurisprudence, while seeking material and spiritual growth for society, has become more pragmatic through custom. Although some Islamic ideals are immutable, political jurisprudence should be considered realistic idealism