The use of palladium catalysts in fused ring synthesis has been increasingly noteworthy in recent years in organic synthesis. It has a lot of potential compared to other transition metal catalysts, because of its one-of-a-kind feature that makes them more widely applicable in a variety of disciplines application. Palladium is important in a variety of Heck processes, including intramolecular, intermolecular, and reductive Heck reactions, which produce diverse carbocycles and heterocycles of biological importance. Under optimal reaction conditions, carbocyclization or heterocyclization occurs, resulting in the production of numerous structural building blocks of naturally occurring compounds. Beside intramolecular Heck-type reactions, cycloaddition, cycloalkylation, oxidative coupling, CÀ H functionalization, cross-coupling reactions, and carboamidation reactions have also been employed extensively to access fused carbo-and heterocycles of immense biological importance. This review article provides a well-summarized discussion (since 2001) on fused carbo-and heterocycle ring synthesis using palladium catalysts, overviewing their applications, and mechanistic insights.