We fabricated fully transparent hafnium indium zinc oxide (HfInZnO) thin film transistors (TFTs) with ZnO:Al(AZO)/Ag/ZnO:Al multilayer source/drain (S/D) electrodes. The effect of Ag interlayer thickness on the electrical and optical properties of AZO(60nm)/Ag/AZO(60nm) multilayer films was investigated. The AZO(60nm)/Ag(10nm)/AZO(60nm) multilayer film shows a low sheet resistance of 10.5Ω/square and a transmittance of 87%. Compared with HfInZnO-TFT with AZO electrode, the performance of the device with AZO/Ag/AZO multilayer electrode was significantly improved. The field effect mobility increased from 3.2 to 5.8cm2/Vs, and the threshold voltage reduced from 2.3 to 0.1V. The improvement was attributed to the lower resistivity of AZO/Ag/AZO multilayer film. The result indicates that AZO/Ag/AZO multilayer electrode is a promising S/D electrode for fully transparent HfInZnO-TFTs.