Cinnamon has a long history both as a spice and as a medicine. This study was carried out to screen the phytochemicals of the extract as well as to evaluate the acute (LD50) and sub-chronic toxicities of aqueous bark extract of Cinnamomum verum in rats. A total of twenty eight rats were used in this study, thirteen for acute toxicity test and fifteen for sub chronic toxicity. The acute toxicity study was done in two phases; in phase I, nine rats were divided into three groups of three rats each and were administered the aqueous bark extract of Cinnamomum verum at different doses of 10, 100 and 1000mg/kg body weight orally. The rats were observed for mortality and general behavior for 24hrs. In phase II, four rats were administered with aqueous bark extract of Cinnamomum verum at higher doses of 1500, 2500, 3500 and 5000mg/kg and were observed for mortality and other signs of toxicity for 24hrs. For the sub chronic toxicity experiment, fifteen rats were divided into five groups of three rats each. Group 1 was the control group, groups II to V were orally administered 50, 100, 150 and 200mg/kg of aqueous bark extract of Cinnamomum verum respectively for four weeks. The rats were sacrificed and blood samples collected for biochemical analysis of liver and kidney functions. The result of phytochemical screening revealed the presence of saponins, reducing sugars, flavonoids, steroids, resins and cardiac glycosides. Acute toxicity revealed that the extract was practically non-toxic with oral LD50 greater than 5000mg/kg body weight. The levels of ALP, ALT, AST and TP of the test groups decreased significantly (p<0.05) with respect to control group while serum TB, ALB increased with respect to control group. A significant decrease (p<0.05) in serum electrolytes, creatinine and urea and an increase in serum bicarbonate was observed in extract administered groups in a dose dependent pattern compared to normal control. In conclusion, these results showed that the extract is rich in phytochemicals and was found to be relatively safe at administered doses