The present investigation focuses on the effect of heat treatment parameters on the hardening and fracture behavior of 17-4 PH stainless steel, thereby assessing the susceptibility to failure at intense loading conditions. The tensile tests were conducted at an effective strain rate of 47 s−1 on a GleebleTM 3800 thermo-mechanical simulator at room temperature and 75 °C. X-ray diffraction (XRD) analyses revealed the presence of a predominant martensitic phase with significant reverted austenite content at higher aging times in the 480 °C condition, thereby resulting in the softening phenomenon and lower strength values. Peak hardness and superior strength values were obtained for higher aging times in the 450 °C condition and lower aging times in the 480 °C condition due to precipitate-particle segregation at packet junctions and finer lath microstructure. Consequently, the fractographic observations from scanning electron microscopy (SEM) exhibited a semi-brittle mode of failure. In the over-aged conditions, a transition toward ductile fracture mode with dimple morphology was depicted. The higher testing temperature produced a uniform set of failure strain values compared to the scattered strains at ambient conditions. © 2022, ASM International.