This work investigates the fatigue strength of multiaxially-loaded gas engine crankshafts incorporating electroslag remelted 50CrMo4 steel. Uniaxial fatigue tests with small-scale round specimens before and after performing the ESR process are conducted. The results reveal that the high-cycle fatigue strength at the run-out region significantly decreases by 21% if no ESR-treatment is performed. Multiaxial fatigue tests under proportional normal and shear stress loading demonstrate that the elliptical model by Gough and Pollard leads to a minor underestimation of 5% compared to the test results. An application of several state-of-the-art equivalent stress hypotheses utilizing the critical plane approach is presented and the estimated results are compared to the experiments in terms of high-cycle fatigue resistance and crack initiation angle.