A rational study has been conducted in order to investigate the effect of an electroless Ni-P coating on the fatigue behavior of two plain carbon steels in the high cycle fatigue regime. It has been shown that a significant increase in the fatigue life of these materials can be achieved in the coated and coated and heat treated specimens in comparison with the behavior displayed by the substrate alone tested under similar conditions. Although no direct measurements of residual stresses have been conducted in the present work, according to previous investigations carried out on this subject, it is possible that significant compressive residual stresses could have been produced in the substrate and could be responsible for the behavior observed. In general, the deposit was observed to remain well adhered to the substrate even after a large number of cycles had been applied. As expected, the increase in the fatigue life of the substrate is much more noticeable at lower alternating stresses applied during the fatigue tests. At elevated stresses the uncoated and coated materials tend to behave in a similar manner. The AISI 1010 steel coated and heat treated samples showed a much more marked increase in the fatigue life than the 1045 samples. However, no conclusive evidence is yet available that allows us to explain such results in terms of the difference in the mechanical strength of both materials.