Nonylphenol (NP) is a widely distributed environment contaminant and has been documented to disrupt testicular development and decrease male fertility. Amongst possible targets of this compound are testicular Sertoli cells, which play a crucial role in supporting and nourishing sperm cells. In the present study, we found that NP treatment could cause dramatic morphological changes as well as decreased cell viability of Sertoli cells, while the following Annexin V-PI staining demonstrated that NP treatment led to increased proportion of cell apoptosis, which was evidenced again by the detection of condensation and marginal changes of chromatins using Hoechst staining and transmission microscopy observation. In addition, increased intracellular Ca(2+) levels and changes of endoplasmic reticulum (ER) ultrastructure were also observed in NP-treated groups, indicating the action of NP on ER. The subsequent data showed that the expressions of ER-stress signaling targeted genes GRP78 and gadd153 were elevated, suggesting the activation of ER-stress signal pathway. Furthermore, the detection of ER-stress related proteins by western blotting revealed that the expression of gadd153 was upregulated by NP, whereas the expressions of GRP78 and ERp57 were both first upregulated and then inhibited. Taken together, it is suggested that NP can induce ER stress in Sertoli cells, which may plays an important role in the induction of apoptosis.