Despite the frequent detection of benzotriazoles (BTRs) and benzothiazoles (BTHs) in groundwater and surface-water environments, knowledge on their occurrence and profile in tap water is still scarce. This study demonstrates widespread occurrence of these compounds in tap water from 51 major cities in China, which have ranges of <LOQ-310 ng/L for ΣBTRs (median: 15.6 ng/L) and 40.1-1310 ng/L for ΣBTHs (median: 406 ng/L). Relationship between BTRs in tap water and influencing factors (e.g., water-source type and gross domestic product of the cities) were discussed. Difference of concentration level and compound profile of BTRs and BTHs in tap water and their surface water source, as well as in wastewater treatment plant effluents, is described. For the first time, different sources of contamination (i.e. from the water source and from distribution systems) are proposed for BTRs and BTHs, respectively. In addition, the contribution of tap water to human exposure to these compounds is assessed.