The paper presents the results of low cycle fatigue studies of WCLV tool steel aimed at determining the diagrams of low cycle fatigue and verifying them based on the analysis of durability of the selected forging tool. Based on the macro- and microstructural tests as well as numerical modelling of industrial forging processes, the conditions for the implementation of laboratory fatigue tests were determined. The samples underwent periodical uniaxial loading (tension–compression conditions) at four levels of amplitude of total strain (0.5; 0.8; 1.0; 2.0%), at three temperatures (20, 300 and 600 °C), based on the macro- and microstructural tests as well as numerical modelling of industrial forging processes. For the determination of the hysteresis loop based on the obtained fatigue results, the Ramberg–Osgood equation was applied. The fatigue diagrams in the bilogarithmic system were approximated by the Manson–Coffin–Basquin equation, and the diagrams of low cycle fatigue in the ɛa–Nf and σa–Nf system were obtained. The results of the laboratory tests concerning the fatigue strength of WCLV tool steel were preliminarily verified based on the analysis of the punch used to forge a lid forging, exhibiting a good agreement. The performed comparative analysis of the results of the fatigue tests and the numerical analysis combined with the studies of the microstructure revealed the possibility of their application in the aspect of forging tools’ durability as well thermo-mechanical fatigue strength.