Abstract—Cinnamon stick is world widely used in cooking, traditional medicine, perfumery and aesthetic industries. Many studies have demonstrated the potential of cinnamon extracts in diabetes treatment. Although it has been reported as safe in general cooking recipe and categorized as GRAS by USDA, sub-acute toxicity procedure was conducted in this study to determine effect of cinnamon extract on histopathological changes as well as the haematological parameters of blood. Water extraction was done for dried cinnamon. Twenty-four female Sprague Dawley rats were used in this study. The oral route was selected because it is the most likely route of human exposure through the consumption of herbs. The concentrations studied were 0.1, 0.5 and 2.0g/kg cinnamon aqueous extract (CE). There were no statistically significant effects of all concentrations of CE on behaviour, mortality, water intake, food consumption, weight gain, internal organs weight (liver and kidney) and heamatological parameters during treatment and post-treatment periods except: 1) the slight decreased in kidney and liver weight of rats treated with 0.5g/kg and 2) slight decreased in liver weight of rats treated with 2.0g/kg, during post-treatment period. Hence, these toxicity studies suggest that the CE is low to moderate in toxicity and CE below 0.5 g/kg dose level is safe to be used in the efficacy study especially for diabetes treatment.