This paper aims to study the microstructure and hardness evolution of the carburized mild steel. The mild steel grade AISI 1020 was employed to be samples with dimension of 5 mm X 25 mm X 2 mmand then packed in the tightly sealed steel container where carburization environment was provided by using mixtures of powdered charcoal and tamarind catalysts. The pack carburizing was performed at carburizing temperature of 950 °C with fixed carburizing time of 2 hrs. The results indicate that pack carburization treatment can favor the formation of the hard phase, which can improve the hardness of samples. The appropriate microstructures of samples subjected to every stage determines the evolution of hardness profiles of the mild steel. The tempering process can improve the toughness of the carburized mild steel. Thus, it should be carried performed after quenching process.