This investigation was carried out to study the effect ferritic-martensitic constituent on mechanical property and corrosion behaviour of medium carbon DP steel. Several stages of heat treatment were applied on the as-received medium carbon steel which composed of lamellarizing, quenching and tempering process. Asreceived medium carbon steel was assigned as a reference sample for comparison analysis. Mechanical property was evaluated using Vickers hardness to examine the effect of changing the ferritic-martensitic constituent of the medium carbon steel. Besides, the effect of this constituent on the corrosive behaviour of the medium carbon DP steel was investigated using 1 M hydrochloric acid solution.