The paper deals with the fatigue and failure analysis of serial shot-peened leaf springs of heavy trucks emphasizing on the influence of thermal treatment and shot peening on fatigue life. Experimental stress–life curves are determined by investigating smooth specimens subjected to fully reversed rotating bending conditions. These test results are compared to corresponding ones determined from cyclic three-point bend tests on shot-peened serial leaf springs in order to reveal the influence of the applied thermal treatment and shot peening process on the fatigue life of the high-strength steel used for leaf spring manufacturing, dependent on the load level. Microstructure, macro- and micro-hardness analyses are performed to support the analyses and explain the effects resulting from the certain shot peening process on the surface properties of the high-strength spring steel under investigation. The assessment of the fatigue results reveals nearly no life improvement due to the manufacturing, emphasizing the necessity for mutual adjustment of shot peening and thermal treatment parameters to take account for life improvement.