Fatigue failures of motor crankshafts operating in thermoelectric power plants are recently being reported. Since crankshafts are subjected to non-trivial stress states throughout their operation, multiaxial fatigue theory is required. A previously carried-out finite element analysis (FEM) that determined the stress states of critical points within the crankshaft’s was used as input. Biaxial stress states were extracted from the FEM analysis and submitted to multiaxial fatigue testing. The fatigue behaviour of the given loading conditions was assessed by using seven multiaxial high-cycle fatigue criteria, namely Findley (F), Matake (M), McDiarmid (McD), Susmel & Lazzarin (S&L), Carpinteri & Spagnoli (C&S), Liu & Mahadevan (L&M) and Papadopoulos (P). An additional set of critical loading conditions was also considered and submitted to both fatigue testing and theoretical predictions. By using experimentally observed fatigue resistance limits, the predictions deliver a slight tendency to fatigue failure in their prediction, in contrast to experimental observations. The results were used to compare the prediction capability of the selected criteria, where all presented reasonably fair agreement. Within the present study’s context, Papadopoulos’ model was the one that presented the least spread in fatigue predictions while also presenting the closest to ideal average behaviour, with the convenient feature of being slightly conservative.