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Metolachlor is a widely used chiral herbicide. However, information on its enantioselective toxicity to earthworms, an important soil organism, remains limited. Herein, the effects of <i>Rac</i>- and <i>S</i>-metolachlor on oxidative stress and DNA damage in <i>Eisenia fetida</i> were investigated and compared. Moreover, the degradation of both herbicides in the soil was also determined. The results showed that reactive oxygen species (ROS) in <i>E. fetida</i> were more easily induced by <i>Rac</i>-metolachlor than <i>S</i>-metolachlor at a higher concentration (above 16 µg/g). Similarly, the effects of <i>Rac</i>-metolachlor on superoxide dismutase (SOD) activity and DNA damage in <i>E. fetida</i> were more significant than those of <i>S</i>-metolachlor at the same exposure concentration and time. <i>Rac</i>- and <i>S</i>-metolachlor did not result in severe lipid peroxidation. The toxic effects of both herbicides on <i>E. fetida</i> gradually decreased after 7 days as the exposure was prolonged. At the same concentration, <i>S</i>-metolachlor degrades faster than <i>Rac</i>-metolachlor. These results suggest that <i>Rac</i>-metolachlor has a greater effect on <i>E. fetida</i> than <i>S</i>-metolachlor, providing a significant reference for the rational use of metolachlor.