Proper heat treatment of steels is one of the most important factors in determining how they will perform in service. Engineering materials, mostly steel, are heat treated under controlled sequence of heating and cooling to alter their physical and mechanical properties to meet desired engineering applications. In this study we have chosen AISI 1020 steel as for our research work and we have tried to find out the mechanical properties (hardness) and micro structural properties (martensite formation, carbon self-locking region) by means of appropriate heat treatment process (annealing, normalizing & hardening). Here the steel specimens were heat treated in a furnace at different temperature levels and soaking time; and then cooled in various media (air, ash, water). After that the hardness of the specimens were rechecked for the comparison with previous data and the microstructures of the specimens were examined using metallurgical microscope equipped with camera. These results showed that the hardness of AISI 1020 steel can be changed and improved by different heat treatments for a particular application. From the microstructures we have found that the annealed specimens with mainly ferrite structure give the lowest hardness value and highest ductility while hardened specimens which comprise martensite give the highest hardness value and lowest ductility. On the other hand, normalized specimens have given the moderate hardness and ductility comparing with hardened and annealed specimens.