The structural, electronic, optical and elastic properties of the cubic double perovskite Cs2CdPbI6 were calculated using a density functional theory DFT. The calculated values were reported to evaluate the photovoltaic (PV) performance of new device structures using the SCAPS-1D solar cell simulation software. The simulation findings demonstrate that the FTO/ETL/ Cs2CdPbI6/HTL which exhibited an efficiency of 32.06%, Voc = 1.4 V, Jsc = 27.99 mA/cm2 and FF = 81.69% at 300 K temperature. The effect of the absorber and ETL thickness, capacitance–voltage, current density–voltage, and quantum efficiency characteristics, series resistance, shunt resistance was also evaluated for the devices. The results of these simulations provide valuable insight that will be useful in the development of efficient double perovskites solar cells based on Cs2CdPbI6.