Objective: Green tea (Camellia sinensis) is one of the most consumed beverages in the world. C. sinensis consumption may prevent tumor and other diseases. Insulinomas are pancreatic islet cell tumors. In present study, the effects of the extract from C. sinensis were investigated in rat insulinoma INS-1 cells. Methods: C. sinensis leaves were collected in Rize, Turkey. The leaves were brewed in tap water for 20 and 40 minutes at 80°C. INS-1 cells were treated with different doses (1-5 mg/mL) of C. sinensis extract for 24 h. Cell viability, proliferation, death were examined. The malondialdehyde, glutathione and protein carbonyl levels were measured in INS-1 cells given C. sinensis extract. Results: The cell viability and the percentage of proliferating cell nuclear antigen immunopositive cells decreased, while the percentage of TUNEL positive cells increased in INS-1 cells treated with the extract from C. sinensis according to control group. While malondialdehyde and protein carbonyl levels in INS-1 cells treated with C. sinensis extract decreased, glutathione levels increased according to control group. Conclusion: The results indicate that the extracts from C. sinensis inhibited proliferation and caused apoptosis in INS-1 cell. C. sinensis may be natural agent for supporting the treatment of pancreatic tumors.