Abstract: Cinnamon is harvested by growing the tree for 2 years then coppicing it. The next year, about a dozen shoots will form from the roots. The branches harvested this way are processed by scraping off the outer bark then beating the branch evenly with a hammer to loosen the inner bark. The inner bark is then prised out in long rolls. Only the thin (0.5 mm (0.020 in)) inner bark is used; the outer, woody portion is discarded, leaving metre-long cinnamon strips that curl into rolls (quills) on drying. Once dry, the bark is cut into 5-10 cm (2.0-3.9 in) lengths for sale. The aim of this study was to evaluation of the cinnamon on dog’s heart performance especially Korotkoff sounds and electrocardiogram. In this study, 10 dogs aged between 2-3 years old were selected by chance. Before onset of the experiment, clinical examination of animals from wellness aspect was done and hearts of each animal from existence of any problem such as congenital or acquired and auscultable murmurs was examined. Then, all animals were fed with cinnamon for 2 weeks. After day 14 and concurrent with last extract administration, electrocardiogram and sphygmomanometric blood pressure obtained from left brachial artery at the times of 2, 4 and 8 h after administration. Then, P-R interval, R wave amplitude, Q-T segment were assayed from electrocardiogram. In the study revealed that cinnamon has protective effect on heart performance because cinnamon improved all measured parameters and researchers recommended use of this medicinal plant but we suggest that more studies required to approving this matter.