Bombyx mori L. larvae were exposed to 4-n-nonylphenol (4-NP) in the laboratory, and their glutathione S-transferase, glutathione peroxidase, and corresponding mRNA levels in gonads during different developmental stages (larval, pupal, and adult) were evaluated. Developmental parameters and glutathione content were also measured. Altered patterns of pupation and adult emergence were observed after exposure to 0.05–0.4 g/kg 4-NP during the entire larval stage. When exposed to 0.4 g/kg 4-NP, the sex ratio (male/female) of the emerged adults increased rapidly from 0.91 ±0.09 to 1.96 ±0.26. A decrease in glutathione content was observed at the larval, pupal, and adult stages. In addition, at 0.05 g/kg 4-NP and higher concentrations, an increase in glutathione S-transferase, glutathione peroxidase activity, and the gene expression level of glutathione S-transferase d1 and glutathione peroxidase were detected in the larval stage, followed by a decline in glutathione S-transferase d1 and glutathione peroxidase transcript levels along with enzyme activity in the pupal and adult stages. The changing trend in mRNA levels of these enzymes was consistent with that of enzyme activity. The results suggest a relationship between 4-NP and alterations in the levels of glutathione-related detoxification enzymes in B. mori gonads.