One of the most significant provisions of a quite large Code of Civil Procedure 1908. We understand this from “Res” meaning subject-matter/dispute and “Judicata” meaning adjudging. The Indian Legal System adopted this doctrine by the way of Section 11 of Code of Civil Procedure, 1908. Section 11 empowers Courts to dismiss suits by a decree of Res Judicata if the issues between the same parties have been adjudged by a competent court under the same factual circumstances. This article delves into the critical analysis of interpretation of the essentials of Section 11, extension of the doctrine in the form of “Constructive Res Judicata” and Relation between Law of Estoppel & Issue Estoppel and Res Judicata. The process of developing conceptual understanding of Section 11 entailed collection and analysis of non-numerical concepts, opinion pieces, commentaries, and papers. Secondary sources like bare acts, books, journal articles, research papers, commentaries and news articles were used. Section 11 of CPC has positioned itself to champion public policy considerations, through cutting the multiplicity of litigations, scope of vexatious litigations, etc.