The influence of Ag doping on the microstructural and superconducting properties of Y3Ba5Cu8O18-delta (Y358) was investigated by means of resistance-temperature ( R-T), ac magnetic susceptibility (chi-T), and X-ray diffraction (XRD) measurements. Five different Y3Ba5Cu8-x AgxO18-delta (Ag-Y358) bulk ceramic samples were prepared by employing a standard solid-state reaction method with different amounts of Ag doping (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5, respectively). The X-ray patterns revealed that all samples corresponded to the orthorhombic Y3Ba5Cu8O18-delta phase. The transition temperature of Ag-Y358 samples was enhanced from 95 to 97 K with the increase of Ag doping concentration (up to x = 0.1). However, when the Ag content exceeded x = 0.3 value, the transition temperature of the samples decreased to below 95.6 K. It was found that excess Ag particles filled into the pores of the structure and caused the deterioration of the superconducting properties.