Background: Heart is a vital organ of circulatory system. Valves maintain the unidirectional flow of blood. Mitral valve (MV) prevents the backflow of blood into the left atrium. For the proper functioning of the heart, all valves should be intact. MV prolapse and regurgitation is the main cause of MV replacement. Mean circumference of MV varies from person to person. Aim of the present study is to measure the average size of the valve in the cadavers of North Karnataka region by using cardiac sizer, which would help in the selection of prosthetic valve in the cardiac surgery. Materials and Methods: This study was carried out on 50 cadaveric adult human hearts. Left atrium was opened along the left border of heart so as to expose the mitral orifice. Then, the diameter of the valve was measured by using cardiac sizer, whereas circumference was calculated manually. Number of mitral valve cusps and papillary muscles were observed. Results: The mean annular circumference and diameter of the mitral valve was found to be 8.03 ± 0.82 cm and 2.56 ± 0.32 cm, respectively. Majority (72%) of the mitral valves had the circumference ranging from 7.53 to 8.47 cm and the diameter ranging from 2.4 to 2.7 cm. Conclusion: The size of mitral valve in the North Karnataka region was found to be less as compared to the other studies. This study might help cardio-thoracic surgeon as well the prosthetic valve manufacturing companies for the rough estimation of the mitral valve size.