The present study explores the usage of acetic-acid-treated cobalt-modified activated carbon as an adsorbent material for the adsorptive desulfurization of DBT-containing model oil. Modification of granular activated carbon (GAC) with acetic acid treatment and incorporation of cobalt species in GAC framework significantly improved its adsorption capacity by improving oxygen-containing functional groups and acidic sites. The surface area of GAC improved from 257 to 393.8 m(2)/g when it was treated with cobalt species and acid. The average size of the Co3O4 crystallites in the Co-loaded activated carbon was found to be 13.8 nm. The effect of various operating parameters such as cobalt loading, adsorbent dose, temperature, and time was studied. Furthermore, the reusability of spent adsorbent and the effect of the presence of other aromatics compounds were also investigated. Under optimized operating conditions, similar to 92% of DBT removal was achieved. The equilibrium data of DBT adsorption were analyzed by Langmuir, Freundlich, Temkin, and Redlich and Peterson (R-P) isotherm models by using nonlinear regression analysis. Among these, the Redlich-Peterson model is the best fit to represent the experimental data. The adsorption of DBT was found to be endothermic in nature. Values of changes in entropy and heat of adsorption were estimated to be 0.177 kJ/(mol K) and 35.67 kJ/mol, respectively. Moreover, a possible adsorption mechanism of DBT was also proposed. Finally, it can be concluded that cobalt-incorporated acetic-acid-activated GAC proves to be a potential adsorbent for the removal DBT from fuel oil in an economic and ecofriendly way.