A systematic study on the effect of silver (Ag) doping in magnesium diboride (MgB₂) superconductor has been undertaken. A series of polycrystalline samples with composition Mg_1-xAg_xB₂ (0 £ x £ 0.20) were synthesized by using the "in situ" solid state reaction method. All the samples were sintered at 850 °C for 2 h under the high purity argon flow. The room temperature X-ray diffraction (XRD), low temperature resistivity (p-T) measurements and field emission scanning electron microscopy (FE-SEM) were performed to explore the phase purity, superconducting transition temperature, and microstructural properties, respectively. The XRD patterns show that Ag doping leads to the formation of Mg-Ag phase. The relative intensity of Mg-Ag phase increases with increasing Ag content. The p-T measurement shows that superconducting transition temperature (T_c) decreases slightly with Ag doping. All the samples have T_c between 38.5K   (x = 0.00) and 37K (x = 0.20). The FE-SEM images have revealed hexagonal shaped grains with an average grain size between 0.20 and 0.50µm.