The pollution level of diuron in seawater and sediments in the west coastal sea area of Zhoushan Island from 2011 to 2013 was investigated. Results revealed that the concentration of diuron in seawater varies from less than (3.0 to 52.1) ng·L^-1, with an average level of less than 11.1 ng^.L^-1. The annual average content was less than 7.9 ng^.L^-1, 13.9 ng^.L^-1, and 12.3 ng^.L^-1 in 2011, 2012, and 2013, respectively. The concentrations of diuron in marine sediments also varied from less than (0.3 to 3.9) ng^.g^-1 (dry weight), with an average concentration of less than 1.13 ng g^-1 (dry weight). The annual average concentration was less than 0.851 ng^.g^-1, 1.328 ng^.g^-1, and 1.202 ng^.g^-1 in 2011, 2012, and 2013, respectively. The accumulation of diuron in seawater and sediments may pose a potential risk to the marine ecosystem of the investigated sea area.