Due to the urgency of our energy and environmental issues, a variety of cost-effective and pollution-free technologies have attracted considerable attention, among which thermoelectric technology has made enormous progress. Substantial numbers of new thermoelectric materials are created with high figure of merit (ZT) by using advanced nanoscience and nanotechnology. This is especially true in the case of metal-chalcogenide-based materials, which possess both relatively high ZT and low cost among all the different kinds of thermoelectric materials. Here, comprehensive coverage of recent advances in metal chalcogenides and their correlated thermoelectric enhancement mechanisms are provided. Several new strategies are summarized with the hope that they can inspire further enhancement of performance, both in metal chalcogenides and in other materials.