The present work demonstrates the effect of the heat treatment process on the microstructure and mechanical properties of dual-phase (DP590) steel. The heat treatment was carried out in two stages. The first stage of heat treatment involves heating the samples above austenitization temperature (825 and 950 °C), followed by quenching. In the second stage of heat treatment, the quenched samples were reheated at 350, 400, and 450 °C for different times. Following that, samples were air-cooled to room temperature. The microstructure of DP590 steel before and after heat treatment was examined by optical and scanning electron microscope (SEM). The X-ray diffraction (XRD) technique was used to study phase analysis. The hardness and tensile properties of as-received and heat-treated samples were evaluated in detail. The microstructure study reveals that the amount of retained austenite increased with increasing reheating temperature. The heat-treated samples showed lower hardness and higher strength than the as-received sample. The yield strength and ultimate tensile strength of DP590 steel were found to be increased with increasing reheating temperature. These results highlight the effect of heat treatment on the microstructural evolution of DP590 steel and, consequently, their effect on the mechanical properties of the alloy. This study will help to obtain a better synergy of the strength and ductility of the steel. .