Polymers play an important role in the fabrication of heterogeneous (nano)catalysts applied for many chemical syntheses and conversions. The excellent properties of polymers, for instance, high thermal stability, large surface area, simplicity of modification and high mechanical strength make them ideal catalyst supports. To reduce the toxicity of metal nanoparticles (MNPs) or complexes, a new method has been developed in recent years for the fabrication of supported MNPs. Synthesis of MNPs or metallic complexes on polymer support has been applied as a prospective solution to avoid the accumulation of waste MNPs in the medium via a recovery process. The blending of nanoparticles with polymers forms nanocomposites with unique properties due to their specific shape, size, and nature. This review is an overview of the current developments in manufacturing, characterization, and applications of cobalt (Co) complexes/NPs decorated on the surface of various polymers for the catalytic oxidation of mercaptans, alcohols, alkenes, etc. using various oxidizing agents such as H2O2, O-2, TBHP (tert-butyl hydroperoxide), etc. Eventually, we envision the current/future challenges and opportunities for these polymer-supported cobalt (nano)catalysts in the field of chemical transformations.