Objective: to investigate the anti diabetic effect of ethanolic extract of Cinnamomum zeylanicum on Alloxan induced diabetes in experimental animals (Rats). Materials and Methods: the alcohol extract of Cinnamomum zeylanicum was tested for its efficacy in Alloxan (150mg/kg) induced diabetic rats. The diabetic rats were divided into 5groups. Group I (control) received 2% gumacasia, group II (positive control) received standard drug Glibenclamide (10mg/kg+ 2% GA), group III, IV, V (T-1 T-2 T-3) were treated orally with a daily dose of 50mg/kg, 100mg, 200mg, respectively for 30 days, for all diabetic rats after giving TEST, NC, PC preparations, the blood samples were collected & the blood glucose levels determined at 0, 1., 0 hr reading is before giving the drug & the remaining three readings after giving the drugs. 24th hr reading is considered as 0hr reading for the next day. Results: administration of alcohol extract of Cinnamomum zeylanicum produced a dose dependent decrease in blood glucose levels in Alloxan induced rats. There was significant fall in blood sugar level in High dose (200mg/kg) in comparison to low dose (50mg/kg) and median dose (100mg/kg) shown by LSD test. This is comparable to the effect of Glibenclamide. Conclusion: the results of this study show that chronic oral administration of an extract of Cinnamomum zeylanicum at an appropriate dosage may be good alternative anti diabetic agent.