Though studies in mechanical behaviour of myocardial tissues have been dominated by left ventricle research, recent findings on certain pathological conditions caused by COVID-19 have changed that outlook and have led to studying other walls of the heart. This paper reports findings of biaxial tensile tests conducted across the three walls of the Wistar rats’ hearts namely left ventricle, septum, and right ventricle. The tensile loads were applied along the directions of the sagittal plane (longitudinal direction), and along the transverse plane (circumferential direction). The atria, pulmonary trunk and all unwanted soft tissues were dissected away. The tests were conducted using a BioTester 5000 CellScalle soft tissue testing machine. Before collecting data, the specimens were preconditioned by applying a 10% strain at a strain rate of 0.001/s. A preload of 5 mN was applied for 0.53 seconds to remove tissue slackness. In order to maintain hydration and mimic the body temperature, saline 0.91% w/v of NaCl was placed in the bath and heated to 37°C and maintained for the duration of testing. The results show that rat myocardium has different tensile properties in the two directions as well as across its three walls.