Oxo-molybdenum chemistry is of great interest since such units are found in the active sites of a majority of molybdo-enzymes. In order to mimic the biological systems, a number of oxo-molybdenum complexes have been synthesised and studied. This review describes synthesis, structure and applications of oxomolybdenum complexes particularly cis-MoO₂(L)(D) where L stands for a dianionic tridentate ONO ligand and D for a donor solvent molecule/monodentate ligand. The ligand moieties are derived from Schiff base, hydrazide Schiff base and other related tridentate ligands L(H)₂. The coordination geometry around the Mo center in these complexes can be best described as a distorted octahedron in which the ONO-tridentate ligand occupies meridional position with two anionic oxygen donors mutually trans and are cis to the oxygen centers of the cis-dioxo group. Mostly the applications of cis-MoO₂-(ONO) type complexes seen in literature are oxo transfer reactions like epoxidation, sulfoxidation and phosphine oxidation reactions.