Abstract: Similar to mammals, the avian heart is a muscular pump responsible for distributing blood throughout the body. However, a larger relative heart weight to body weight (RHW/BW) was reported in birds than mammals. Furthermore, it has been revealed that smaller birds specially flying one have relatively larger hearts (relative to body mass) than larger birds (non-flying). Although this fact, there are no literatures regarding comparative descriptive variations of the heart in flying and non-flying birds that could adapt various functions, such as flying and running. Therefore, this study aimed to conduct a comparative anatomical features and morphometrical measurments between the hearts of pigeon and fowl. The present study also analyzed the immunohistochemical expression of Troponin T (TnT) as one of the major regulator of striated muscle contraction. The study revealed significant larger RHW/BW in pigeon heart. Furthermore, the hearts of both fowl and pigeon are directed caudoventrally in the cranial part of thoracoabdominal cavity, however, a more oblique position nearly parallel to the sternum was observed in pigeon`s hearts. Interestingly, the mean morphometric values (length of both cranial and caudal borders, diameter of the base, and thickness of both right and left ventricular wall and interventricular septum) of the pigeon hearts showed significant higher differences than that of fowl. Additionally, more expression of TnT was observed in pigeon hearts. Therefore, our findings suggest that such morphological and immunological varities are possibly essential factors for providing intense ventricular contraction of the pigeon`s heart to cover the high metabolic requirments for flight.