The organic alkylphenol 4-nonylphenol (NP) is regarded to be an endocrine disrupting chemical (EDC), one of the widely diffused and stable environmental contaminants. Due to its hydrophobicity and long half-life, NP can easily accumulate in living organisms, including humans, where it displays a series of toxic effects. It has been widely reported that NP affects male reproduction. In addition, there is increasing evidence suggesting that NP is detrimental to various organs, including the pancreas. This study investigated the adverse effects of NP exposure on the pancreas. Sprague-Dawley rats were treated with different doses of NP for 90 consecutive days. The data suggested that the body weights of the rats treated with NP decreased, and the highest dose of NP treatment (180 mg kg-1) dramatically increased water consumption by rats. Meanwhile, H&E staining and immunohistochemistry indicated that islets in the pancreases shrunk when the rats were treated with the indicated doses of NP. TUNEL staining demonstrated that NP exposure up-regulated the level of apoptosis in the pancreases in a dose-dependent manner. Besides this, NP exposure inhibited the secretion of insulin and disrupted glucose tolerance. The levels of reactive oxygen species (ROS) and intracellular calcium ([Ca2+]i) in the islets were up-regulated in the groups of rats treated with NP, but the levels of Mitochondrial Membrane Potential (MMP) were down-regulated. These results suggest that NP-induced pancreatic damage in rats occurs through mitochondrial dysfunction and oxidative stress, which causes disruption of glucose tolerance and decrease in insulin secretion.