This work presents a study and comparison of the effect of shot-peening (SP) and low-plasticity burnishing (LPB) on the high cycle fatigue of a DIN 34CrNiMo6, quenched and tempered, steel. Additionally, this work also provides data, coefficients, and procedures for the fatigue design and analysis of components treated by SP and LPB. Four sets of specimens have been tested to obtain alternating bending S-N curves, namely, machined, mirror-polished, and SP and LPB treated specimens. Compared with the machined specimens, the fatigue limit of the SP specimens increased by 39%, whereas that of the LPB specimens increased by 52%. Attention has been given to the measurement of the surface and in-depth residual stress field of the SP and LPB specimens, including a study on the relaxation of the surface residual stresses under cyclic load and the development of a model to predict the evolution of residual stresses with time.