Abstract Fatigue failure is the most common failure in engineering parts. Therefore, effect of deep cryogenic treatment on the fatigue strength of 1.2542 tool steel has become important. In this study, two groups of specimens were used to investigate fatigue behavior; only one of these groups underwent deep cryogenic treatment in liquid nitrogen for 4 h after hardening treatment in water. The results showed that fatigue limits of both groups were approximately the same; however, scatter of fatigue data was less in the deep cryogenic specimens. Thus, in design process, deep cryogenic specimens can be used with more reliability coefficient; therefore, dimensions of engineering parts are reduced.