Worldwide interest is growing in the various catalytic uses of cobalt/cobalt oxide nanoparticles in the synthesis of heterocyclic compounds. This review covers the last seven-year (2017–2023) reports on the catalytic applications of cobalt/cobalt oxide nanoparticles in heterocyclic compounds. For several chemical reactions involving N-Heterocycles, we described Co/CoO nanoparticles that were doped with other elements and coordinated with nitrogen in the current work. An excellent performance for reversible hydrogenation-dehydrogenation processes is attributed to a well-designed Co metal catalyst with a reductive N-formylation of N-heterocyclic arenes, an organic pathway for hydrogen storage. There have also been reports of various MCR for heterocycles utilising Co/CoO NPs as the catalyst. In addition to the solvent-free, selective aza-heterocycle synthesis using cobalt described above, intra-molecular ring-closing processes for the synthesis of organic heterocycles have also recently been discovered. In this context numerous studies on a variety of topics, including the oxygenation of alcohols to aldehyde, esters, and nitriles, aryl halide biaryl coupling reactions, radical trans-annulations, multicomponent coupling reactions, cyclization, and cyclo-propanations have been described.