Room-temperature thermoelectric materials provide promising solutions for energy harvesting from the environment, and deliver a maintenance-free power supply for the internet-of-things (IoTs). The currently available Bi₂Te₃ family discovered in the 1950s, still dominates industrial applications, however, it has serious disadvantages of brittleness and the resource shortage of tellurium (1 × 10⁻³ ppm in the earth's crust). The novel Mg₃Sb₂ family has received increasing attention as a promising alternative for room-temperature thermoelectric materials. In this review, the development timeline and fabrication strategies of the Mg₃Sb₂ family are depicted. Moreover, an insightful comparison between the crystallinity and band structures of Mg₃Sb₂ and Bi₂Te₃ is drawn. An outlook is presented to discuss challenges and new paradigms in designing room-temperature thermoelectric materials.