This work deals with the effect of Sn doping at mole percentages of 1 %, 2 %, 3 % and 4 % on the structural, morphological, and optical properties of Co3O4 thin films. These physical properties were carried out by X-Ray Diffraction (XRD), Raman, Atomic Force Microscopy (AFM), scanning electron microscope (SEM), Ultraviolet-Visible-Near infrared spectroscopy (UV-Vis-NIR) and spectroscopic ellipsometry (SE). Co3O4 thin films were grown on amorphous glass substrates by spray pyrolysis technique. Experimental and modeling rigorous studies using these different techniques particularly SE were achieved in order to determinate the effect of tin doping on physical properties of cobalt oxide thin films. The incorporation of Sn into the Co sites affects drastically the optical transitions values as well as other optical properties such as the dielectric function, the band gap, the refractive index and the extinction coefficient. All doped samples exhibited a relatively higher absorption coefficient compared to the undoped ones, greater than 105 cm−1 over a wide energy range. SE analysis revealed a smaller transition of approximately 0.77 eV considered as fundamental band gap energy that was assigned to a 3d-d type within the Co2+ tetrahedral site.