Triclosan as an important antimicrobial agent is increasingly detected in the terrestrial environment as sewage sludge and reclaimed water are applied on land, but little is known about its effect on non-target soil organisms. In this study, biochemical responses including changes in the activity of catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST), and malondialdehyde (MDA) of the earthworm Eisenia fetida were examined in order to assess ecological toxicity of the chemical. The single-cell gel electrophoresis (SCGE) was also used to measure the potential genotoxicity of the chemical. The results showed that the activity of CAT and GST at the highest tested dose could be stimulated after a 2-d exposure, reaching 148% and 123% of that in the control, respectively. However, with prolonged exposure, the activity of CAT and GST at the highest tested dose was inhibited, falling to 47% and 33% of that in the control, respectively. Triclosan induced an increase in the activity of SOD, but no significant (p>0.05) changes were observed. The content of MDA was dependent both on the dose of triclosan and on the exposure duration. The comet assay demonstrated that triclosan treatments led to a dose-dependent DNA damage of E. fetida after exposures of 7 and 14 d. Our findings can suggest that triclosan has sublethal effects on E. fetida.