Sodium-carbonate-promoted green and facile synthesis of 5-amino-1,2,4-thiadiazoles and 5-amino-1,2,4-selenadiazoles with elemental sulfur and selenium, respectively, was developed. This method was carried out with O2 in the air as the green oxidant, and it has several advantages, including low cost, low toxicity, and stable sulfur and selenium sources, high atom efficiency with water as the sole byproduct, simple operation, and broad substrate scope. Preliminary mechanistic studies indicate that the formation of 1,2,4-thiadiazole ring and 1,2,4-selenadiazole ring undergoes different processes.