The protective effect of sesamin (SES) from sesame meal on NIT-1 pancreatic β-cells damaged by streptozotocin (STZ) in vitro was investigated. The cell viability, insulin secretion, the activity of superoxide dismutase(SOD), glutathione peroxidase (GSHpx) and the content of reduced glutathione (GSH) increased significantly when incubated with SES (400, 200 µg mL-1). The content of malondialdehyde (MDA), nitric oxide (NO) production, and the activity of NO synthase (NOS), inducible NOS (iNOS), decreased significantly when incubated with SES. The destructive changes of NIT-1 cells were ameliorated when treated with SES under microscopic observation. These data suggested that SES had obvious protective effect on NIT-1 pancreatic β-cells damaged by STZ, which might be related to its effects of decreasing levels of β-cell-destroying factors such as oxidative stress and NO synthesis.