Many structural components such as pipings and pressure vessels experience plastic deformation during final cold forming required by joining threaded or welded connections. The effect of prior plastic strain on further resistance to fatigue is scarcely documented in open literature regarding high strength martensitic steels, and controversial effects have been reported. This work addressed the effect of prior tensile plastic strain on the residual fatigue lifetime and on fatigue crack initiation and propagation mechanisms of a high strength martensitic steel. Polished low cycle fatigue specimens were tested with or without prior tensile deformation up to 4%. Specimens were also cut from an actual component that experienced cold forming up to a few % followed by stress relieving. Manson-Coffin curves were determined for each strain path; damage and fracture mechanisms were investigated using both 2D (scanning electron microscopy) and 3D (X-Ray tomography) techniques. Miniaturized crack propagation specimens were also extracted from the undeformed material and from tensile specimens previously deformed up to 4%, then tested in fatigue. All stress-strain curves exhibited cyclic softening together with Masing effect; stress amplitudes vs. cycle numbers quickly merged into a single curve until damage development. Prior tensile deformation induced a slight decrease in lifetime, with no change in the Manson-Coffin exponent. The amount of cumulative plastic strain at fracture significantly decreased after prior plastic deformation, whereas the fatigue crack propagation rate increased by about 20%. These phenomena did not depend on the prior deformation conditions. Several fatigue cracks initiated from persistent slip bands at the side surface of low cycle fatigue specimens. They propagated independently toward the specimen axis, extending up to 25% of the specimen gage radius. Even after deep crack propagation, the specimens failed in a ductile manner by final pulling at temperatures as low as -80°C. Fatigue striations were detected in fracture surfaces of the crack propagation specimens. Some smooth regions were also detected, also linked to the crystallography of martensite packets but without any sign of cleavage fracture. Under higher stress intensity factors, the density of secondary cracks increased, the fraction of smooth regions decreased and the presence of slip bands in these regions became more visible. Whatever the type of cyclic test, damage and fracture mechanisms did not vary with the application of prior tensile strain. Prior tensile plastic deformation proved an efficient tool to assess the residual fatigue strength of the considered high-strength martensitic steel.