This paper presents a novel method for growing thin films of Cu2SnS3 (CTS) using a solution-based chemical route consisting of simultaneous precipitation of Cu2S and SnS2 performed by diffusion membranes assisted CBD technique. Diffusion membranes are used to optimize the kinetic growth through a moderate control of release of metal ions into the solution. As the conditions in terms of concentration of metal species, sulphide anion and temperature required for the formation of the Cu2SnS3 compound have not yet been reported by other authors, in this paper we propose a way to achieve these, through a study of the chemical equilibrium of the system SnCl2, Na3C6H5O7¿2H2O, CuCl2 and Na2S2O3¿5H2O. These conditions were obtained solving the equilibrium equations with the help of the Visual MINTEQ 3.0 package, supported on the program MINTEQA2. X-ray diffraction (XRD) and Raman spectroscopy techniques were used to confirm the formation of the Cu2SnS3 phase.