The structural analysis of a cobalt(III) complex [Co(HL)₂](OAc)·H₂O (1) [H₂L = N-(2-hydroxyethyl)-3-methoxysalicylaldimine] reveals a tridentate chelation behaviour of the ligand H₂L having a distorted octahedral coordination environment around the cobalt(III) center with a CoN₂O₄ chromophore. 1 behaves as an effective catalyst towards the oxidation of 3,5-di-tert-butylcatechol in different solvents, viz. dichloromethane (DCM), methanol (MeOH) and acetonitrile (MeCN) to its corresponding quinone derivative in aerial oxygen. The reaction follows Michaelis–Menten enzymatic reaction kinetics with turnover numbers (K_cat), 1.46 × 10³, 1.21 × 10³ and 2.16 × 10³ h⁻¹ in DCM, MeOH and MeCN, respectively.