Triclosan is an antimicrobial agent that is extensively used in various consumer care products. It entered the aquatic environment, mainly through municipal and industrial effluents, which acted by hindering one of the highly conserved enzymes of bacterial fatty-acid biosynthesis. It was noted that laccase could catalyze one-electron oxidation of phenolic pollutants into radical intermediates, and subsequently coupled to each other via the covalent binding. In this study, the transformation of triclosan in aqueoussolution was investigated by laccase-mediated enzyme-catalyzed oxidative coupling reactions (E-COCRs) in the absence and presence of 1-hydroxybenzotriazole (HBT, a redox mediator). The transformation products of triclosan were identified using high-resolution mass spectrometry (HRMS), and the transformation mechanism of triclosan was also proposed. Results indicated that laccase from Pleurotus ostreatus was effective in removing triclosan, and the presence of HBT significantly improved triclosan removal. The reactions followed the apparent pseudo first-order kinetics during 0~4h incubation (R² ≥ 0.9465), the rate constant (k) values were respectively 0.43 and 0.95/h in the absence and presence of HBT, and the removal half-life (T_1/2) values were 1.60 and 0.73h, respectively. The oligomerization (dimers, trimers and tetramers) of triclosan was identified as the dominant reaction pathway by laccase without HBT present, whereas the ether cleavage led to triclosan decomposition (2,4-dichlorophenol and 3-chlorophenol) in the presence of HBT was the predominant pathway. These findings presented in this study provide a novel insight into the fate and transformation of triclosan by laccase-mediated E-COCRs in aquatic environment in the absence and presence of HBT.