The polycrystalline Cu0.5Ag0.5InSe2 thin film was deposited on mono-crystalline n-Si wafer by sequential thermal evaporation of elemental sources. p-Cu0.5Ag0.5InSe2/n-Si heterojunction diode was fabricated and the current-voltage characteristics of the diode at various temperatures were investigated to determine the main diode parameters and dark current transport mechanism. The studied diode structure showed a rectifying behavior with a barrier height of 0.63 eV at room temperature. Series and shunt resistance values were calculated by parasitic resistance relations in high bias regions. Considering the ideality factor values between 1.7 and 2.8, dominant transport characteristics were detailed for forward and reverse voltages. The analysis of the forward current-voltage behavior reveals field emission can be the possible current conduction mechanism. At the reverse bias region, around 10(1) number of tunneling step and about 10(5) density of traps were found to act a role in the process in leakage current flow.