In this research, the heat-treatment effect on the mechanical properties of free-cutting steels was investigated. Free-cutting steels (FCSs) are used where high degrees of machining are required as they increase the machining speed and reduce the tool wear. The effect of heat treatment on mechanical properties was identified using tensile and fatigue tests, and microstructure images taken with a scanning electron microscope (SEM). The studied material included commercially available AISI 12L14 cylindrical bars of free-cutting steel. FCS was heated to 900 degrees C and held at this temperature for different time spans. The degradation of the mechanical properties of free-cutting steel due to the elevated temperature was assessed. At a microscopic level, more mechanical damage was observed between the steel matrix and the second phase of the heat-affected specimens.