Estimation of heart fatty acid-binding protein (FABP3) levels in cardiac tissue may have a value in the identification of myocardial injury as a cause of electrocution death. The aim of the work: To investigate for the first time the post mortem mRNA expressions of heart fatty acid-binding protein (H-FABP) by qRT-PCR in the heart and brain of electrocuted rats at different post mortem intervals (PMI). Methods: Sixty adult male Sprague Dawley rats were allocated into two main equal groups, G1: control (C): exposed to cervical dislocation and G2: exposed to fatal electrocution (EC) (220 V, 50 Hz, 60 sec). Both groups were subdivided into (C0, C4, C8), and (EC0, EC4, EC8) respectively, corresponding to 0, 4, and 8 h PMI in the C and EC groups. Results: The H-FABP mRNA expression levels were significantly up-regulated in the heart and brain of the EC group (8.59±1.27, 2.25±0.13) compared to the C group (3.35±0.51, 0.96±0.05) respectively. H-FABP expression levels were significantly up-regulated with PMI prolongation either in the heart (3.23±1.04, 5.25±1.40, 7.93±1.98) or in the brain (1.46±0.21, 1.61±0.33, 1.75±0.38) at 0, 4, and 8 h. The interaction between PMI and treatment showed a significant effect on H-FABP mRNA expression levels between EC groups in the heart (5.43±0.12, 8.22±0.06, 12.13±0.04) and brain (1.89±0.03, 2.31±0.03, 2.55±0.07) compared with the C groups in the heart (1.04±0.08, 2.28±0.01, 3.73±0.02) and brain (1.04±0.08, 0.90±0.01, 0.95±0.02) respectively at 0, 4, and 8 h. Conclusion: The H-FABP mRNA expression could be employed as a sensitive detective biomarker for estimation of PMI in cases of electrocution fatalities.