In this study, failure analysis of an axle shaft in an airport ground support vehicle was carried out to determine failure mechanism, failure root causes and preventive actions. Macroscopic observation, numerical analysis, metallographic analysis, chemical composition analysis, hardness measurement and tensile test methods were used in failure analysis. In numerical fatigue analyses, axle shaft was modelled as a functionally graded material due to mechanical properties changing in the material radial section as a result of induction surface hardening. The analysis results showed that the failure mechanism of fractured axle shaft was torsional fatigue. High surface roughness and insufficient mechanical properties were found as failure root causes. Making finish cut with low depth and even grinding in surface finishing process were proposed as a prevention to increase surface quality, reduce surface roughness and stress concentrations in machining of axle shaft. In addition, using another material with higher yield strength (EN 37Cr4) was proposed instead of EN 34Cr4 alloy steel as the axle shaft material.