This paper presents a graphene oxide-based magnetic nanocomposite as a catalyst for desulfurization and also as a sorbent for removal of the total sulfur in liquid fuel matrices. The magnetic nanocomposite was prepared by decorating graphene oxide nanosheets with magnetite nanoparticles (MGO). For the desulfurization experiments, an oxidation-extraction procedure was developed using MGO as the catalyst and H2O2 as the oxidant. For the sulfur determination experiments, the oxidized-sulfur compounds were sorbed by magnetic solid phase extraction (MSPE) followed by ICP-OES detection. The magnetic nanocomposite showed high efficiency as did both the catalyst of sulfur compounds oxidation and the adsorbent of the oxidized sulfur compounds. Different parameters which could affect the desulfurization and determination were optimized using a multivariate analysis. The results showed that under the optimum conditions removal efficiencies of over 97% were achievable and the limit of detection of 0.15 mg kg(-1) of sulfur was obtained. Finally, the spiked/recovery assays of commercial fuel samples using MSPE-ICP-OES led to recovery values in the range of 94 +/- 5% to 101 +/- 3%. The results obtained suggest that a powerful alternative has been developed for the desulfurization and total sulfur determination in commercial fuel samples.