Heart is a critical organ, composed of cardiac muscle, which is responsible for pumping blood throughout the blood vessels in the whole body. Heart disease is the leading cause of death and disability in both industrialized nations and the developing world, accounting for approximately 40% of all human mortality. Cardiac tissue engineering is one of the most promising strategies to reconstruct the infarct myocardium and the major challenge involves producing a bioactive scaffold with anisotropic properties that assist in cell guidance to mimic the heart tissue. According to anisotropic and nonlinear elasticity of heart muscles, elastic scaffolds with mechanical properties similar to heart muscle are important in cardiac tissue engineering to provide mechanical support to the heart throughout the beating processes. Polyester urethane (PEU) and polyester urethane urea (PEUU) were synthesized for fabrication of scaffolds in this study due to their biodegradability, elasticity and mechanical properties. Gelatin also was blended with PEU and PEUU for modification of hydrophilicity and biodegradability of resultant scaffolds. Solutions of PEU/gelatin and PEUU/gelatin with ratios of 100/0, 70/30 and 50/50 were electrospun to fabricate random nanofibrous scaffolds. Aligned PEU/gelatin and PEUU/gelatin nanofibrous scaffolds with ratios of 100/0 and 70/30 were also produced. Attenuated total re?ectance Fourier transform infrared (ATR-FTIR) spectroscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD) analysis were used for characterization of the synthesized PEU and PEUU and properties of nanofibrous scaffolds were evaluated using field emission scanning electron microscopy (FE-SEM), FTIR, contact angle measurement, biodegradation test, tensile measurements and dynamic mechanical analysis (DMA). Morphology and average diameter of nanofibrous scaffolds were studied by FE-SEM and showed that, fiber diameter significantly decreased, with increasing the concentration of gelatin in PEU/gelatin and PEUU/gelatin blend polymeric systems. Also no signi?cant differences in the diameter were observed for random compared to aligned nano?bers. FTIR spectra showed that there were no interaction between PEU and gelatin and also between PEUU and gelatin. Results of contact angle and degradation analysis indicated that by increasing of gelatin in the polymer blends, hydrophilicity and degradation of resultant nanofibrous scaffolds increased . Tensile strength analysis were performed in both wet and dry conditions revealed that, tensile strength and modulus decreased and elongation increased for nanofibrous scaffolds containing gelatin in wet condition. The tensile properties of aligned nanofibrous scaffolds in both parallel and perpendicular to the fiber direction was found to be significantly different and suggest that aligned nanofibrous scaffold, can achieve desirable anisotropic mechanical properties, which closely match the requirements of native cardiac anisotropy. Dynamic mechanical analysis showed that no significant differences were found in the storage and loss modulus of nanofibrous scaffolds by increasing frequency in the frequencies of the physiological activity of the heart. Storage modulus and loss modulus in different directions of aligned nanofibrous scaffolds were also different indicating anisotropic properties of the aligned nanofibrous scaffolds. Moreover, anisotropic properties of the aligned nanofibrous scaffolds were not changed, by increasing the temperature from 25 ?C (ambient temperature) to 37 ?C (body temperature). According to the results, aligned PEU/gelatin (70/30) and PEUU/gelatin (70/30) nanofibrous scaffolds were found to be more suitable substrate for cardiac tissue engineering due to their similarity to anisotropic mechanical properties of heart. Key Words: Cardiac tissue engineering, Elastomer, Polyurethane, Gelatin, Nanofiber, Anisotropy, Dynamic mechanical properties.