The hearts of males of 1-3-years of age extracted from carcasses (tigers, which died due to various causes in the natural habitat) served as material. Morphometric indicators were calculated by means of a measuring ruler and a caliper. Measurement parameters were the length of the heart, from the point of origin of the aorta to the apex; width, distance between lateral surfaces of the heart at the level of the base of the ventricles; and the thickness of the front and rear segment, at the level of the base of the ventricles heart length. After the measurements of the main components of the heart the number, location, size and individual characteristics of the internal stmctures such as scallop muscle, fleshy trabeculae (bridges and rail), the structure of the valve apparatus (papillary muscle, atrioventricular valves folds, strings) were defined). The length of the papillary muscle was determined by the distance from the middle of the base to the top width and cross-sectional dimension at the middle of it. Thus, there are two types of the Amur tiger’s heart at the age of 1-3 years: elliptical and spherical. The location of pectinate muscles in the left atrium in general is similar to their location in the right, however, in the left atrium, their number is smaller with a larger width. Mammillary muscles of the right ventricle from the wall have a cylindrical and conical shape, in addition to the core muscles, there are also incremental, small size. Fleshy trabeculae is well developed on the surfaces of the walls and the septum. In the left ventricle mammillary muscles are well developed, parietal locations, they have between 2-7 heads, which are attached to the strings of the valves.