Organophosphate esters (OPEs) in the environment, especially in source water, pose a potential threat to both human health and aquatic organisms. This study investigated the concentration, seasonal difference, and risk of 14 widely used OPEs in river and reservoir source water in South China. The total concentration of OPEs was significantly higher during the dry season than during the wet season (p<0.05; median: 144 ng/L vs. 89.4 ng/L). The most dominant OPEs among the 14 investigated in source water were tris(1-chloro-2-propyl) phosphate (TCIPP) during the dry season. No significant difference was found in the concentration and profile of OPEs between the river and reservoir source water investigated (p>0.05). The health risk of OPEs in the source water to humans was negligible (non-carcinogenic risk <1; carcinogenic risk <10-6) with the dominant contributor being tris (2-chloroethyl) phosphate (TCEP). The environmental ecological risk of OPEs was mostly low (risk quotient <0.1) in the source water investigated. Overall, the source waters in South China were found to be relatively safe for use as drinking water sources in the context of OPE pollution.