Bismuth telluride has been the only thermoelectric material having thermoelectric figureof- merit (Z1) of - 1 at room temperature since its discovery in 1950s and is still the only thermoelectric material having been commercialized in large scale for cooling applications. Now we discovered comparable ZTs at room temperature il MgAgSb-based materials MgAgo.97Sbo.99 and MgAgo.96sNio.oo5Sbo.99 through synthesis proce s and composition optimization. The materials are made by ball milling powders of elemedts in a two-step process and hot pressing the final powders into dense bulk samples. The dense bulk materials consist of grains smaller than 20 run, which is one of the main reasons for the very low thermal conductivity of -0.7 Wm- 1 K-1 at room temperature_ The ZTs at room tempt ature are close to I and increase with temperature to a maximum of -1.4 at 475 K. Our disca 1 very opens a door to a possibly beginning of a new era of new thermoelectric materials with high fZTs at around room temperature.