Indoor air quality is of importance for human health since people spent most of their time indoors. Heavy metals (HMs) in indoor air should be concerned since they may increase the incidence of various diseases. However, systematic studies on the occurrences, sources, and health risks of HMs in indoor air were insufficient. Herein, HMs in indoor air were systematically reviewed at a global scale, the characteristics of HMs in different regions, functional areas, and building types were investigated. The results showed that frequent traffic and indoor smoking made Zn occupy the dominant position of HMs in indoor air, accounting for 69.72 %. In rural areas, indoor As and Pb were 1-2 orders of magnitude higher than those in other areas due to burning of inferior fuels. In addition, cooking activities could increase Pb concentrations in residential buildings, reaching 755.32 ± 6556.82 ng/m³. Health risk assessments showed that residents in Southeast Asia and East Asia were at non-carcinogenic risk from multiple HMs (HQ > 1). The use of solid fuels and industrial emissions were the main reasons. This study confirmed the importance of controlling indoor air pollution to reduce its health impact, which can provide useful information for policy makers.