Semiconductor oxides are a class of materials used in many different applications, such as catalysis, solar cells and magnetic devices. In particular, composites with different semiconducting oxides follow synergetic effects with changes of electrical conductivity or magnetic properties. In this case, the synthesis conditions are very important for controlling their properties due to structural defects and non-stable phases at room temperature. In this paper, we analyzed the influence of the synthesis temperature and different concentrations of cerium in the formation of the orthorhombic SnO₂ phase. The structural and morphological characterization was performed using experimental techniques such as X-ray diffraction (XRD), allied with Rietveld refinement, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). The reflections in the XRD pattern and clear lattice fringes observed by HRTEM confirm the formation of the orthorhombic SnO₂ phase in the (Sn_1−xCe_x)O₂ with x = 0, 0.05, 0.1 and 0.3 synthesized at 750 °C. The reducing atmosphere generated by the heat treatment process of the samples and the strain originated due to the difference of ionic radii between the tin and cerium ion can play a crucial role in the formation of the orthorhombic phase of SnO₂.