© 2020 Elsevier Inc. Benzotriazole (BTR) is a common corrosion inhibitor used to protect copper (Cu) and Cu alloys. To reveal the combined subacute toxicity of BTR and Cu at environmental levels on terrestrial animals, the activity of antioxidative enzymes and the glutathione levels in earthworms (Eisenia fetida) of the single or co-exposure treatments were determined. The activity of both antioxidant enzymes and non-enzymatic antioxidants was affected by BTR in earthworms. Moreover, the analyses of lysosomal neutral red retention time and total antioxidant capacity indicated a detoxification effect of BTR on Cu-induced impairments of the antioxidant defense capacity in earthworms. The apoptotic rate of coelomocytes in earthworms of the co-exposure treatment was lower than that in earthworms treated with Cu only, indicating that BTR alleviates Cu mediated lysosomal membrane damage and antioxidant defense system responses in earthworms.