In this article, a p-type and n-type of CdSe thin film were used as a fundamental component of the solar cell used the SCAPS. The current study is to investigate the effect of environmental parameters such as temperature and illumination intensity on the performance of the proposed cell composed of (ITO/n-CdSe/p-CdSe/Pt). Simulations were carried out for various value of temperature ranging from (240 to 500) K and various levels of illumination ranging from (200 to 1200) W.m^-2. The findings revealed that the open circuit voltage is the most temperature-affected parameter, as the open circuit voltage drops from (1.0836V) at 240^oK to (0.6656V) at 500^oK with rising temperature, due to the saturation current decreasing with increasing temperature. The results also reveal that the intensity of illumination has a significant impact on the short-circuit current density, since the current density increases directly with the intensity of illumination from (4.02 mA/cm²) at 200W.m^-2 to (24.13 mA/cm²) at 1200W.m^-2. These findings are discussed in this study.