Commercial hot extrusion is a billet-by-billet cyclic process, with high thermal and mechanical stresses generated in the die set. The die is a costly piece of equipment, and its long service life is essential for profitable operation. Extrusion dies primarily fail by fracture, wear, and plastic deformation. To avoid early failure, it is essential to have an optimum combination of toughness and hardness in the die. This combination can be achieved through a judicious mix of heat treatment and surface hardening. Experiments were conducted to determine mechanical properties of H13 steel after various heat treatment sequences. Heat treatment strategy is described in detail, and effect of different tempering temperatures on fracture toughness and hardness of the tool steel is reported. Changes in mechanical properties are also related to the variation in microstructure. For use in commercial hot extrusion dies, optimum tempering temperature for H13 steel was found to be near 525-600°C, for the best combination of toughness and hardness.