In the present investigation, effects of ethanolic extract of Nigella sativa seed extract on insulin resistant non insulin dependent diabetic (NIDDM) guinea pigs were studied. Significant (p<0.05) decrease in blood glucose level and glycosylated haemoglobin were observed in animals treated with ethanolic extract of N. sativa. In addition, improvement in glucose tolerance, insulin level and insulin sensitivity was observed in treated diabetic animals. The results were more significant in animals treated with higher dose of N. sativa seed extract (500mg/kg BW) as compared to lower dose of extract (250 mg/kg BW). Protective effect of N. sativa seed extract was comparable to the standard drug (i.e., glimepride). Therefore it is concluded that N. sativa seed extract might prove beneficial in preventing hyperinsulinemia, impaired glucose tolerance, insulin resistance and eventually an effective means of improving hyperglycemia, without any toxic effect at the doses studied in the present study.