The objective of this study was to determine the occurrence of triclosan in the tropical rivers where received the effluents from a hospital wastewater treatment plant (HWWTP) in southern Taiwan. Three and ten sampling sites were selected at the Jiaosu River (S0-S2) and Dian-Bao River (S3-S12), respectively. The samples of the HWWTP influent, effluent and receiving river water and sediment were collected and analyzed using ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/ MS). Results showed that the triclosan level in surface water of the Jiaosu River and Dian-Bao River ranged from 3 to 68 ng/L and ranged from <2.7 to 51 ng/L, respectively. The hospital did contribute a loading of triclosan to the neighboring river. The mean value of triclosan concentration in the downstream surface water of the Jiaosu River (S1 20.2 ng/L) was approximately three times higher than that of the background level (S0 6.0 ng/L) (p = 0.011). The concentrations of triclosan in two surface water samples were over the predicted no effect concentration (PNEC) of 50 ng/L for algae. In addition, significant seasonal differences of triclosan in surface water of Jiaosu River (p = 0.020) and the HWWTP effluents (p = 0.302) were also observed. The concentrations of triclosan in sediments of these two rivers seemed stable. On average, triclosan was detected in 86 % of the sediment samples with a range from <1.1 to 13 ng/g. Triclosan in surface water and sediments of the tropical rivers might be rapidly photolyzed due to plenty of sunshine. It is worth to further investigate the occurrence and fate of triclosan photoproduct in the aquatic environment of the tropics.