Saturn is the only known planet to have co-orbital satellite systems. In the present work we studied the process of mass accretion as a possible mechanism for co-orbital satellites formation. The system considered is composed of Saturn, a protosatellite and a cloud of planetesimals distributed in the co-orbital region around a triangular Lagrangian point. The adopted relative mass for the protosatellite was 10-6 of Saturn's mass and for each planetesimal of the cloud three cases of relative mass were considered, 10-14, 10-13 and 10-12 masses of Saturn. In the simulations each cloud of planetesimal was composed of 103, 5 x 103 or 104 planetesimals. The results of the simulations show the formation of co-orbital satellites with relative masses of the same order of those found in the Saturnian system (10-13-10-9). Most of them present horseshoe-type orbits, but a significant part is in tadpole orbit around L(4) or L(5). Therefore, the results indicate that this is a plausible mechanism for the formation of co-orbital satellites.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)