The sources of measurement uncertainty for nitrided case depth with hardness method are analyzed. Moreover, the measurement uncertainty of nitrided case depth is evaluated in detail by synthetic evaluation method. The influences of boundary Vickers hardness value on evaluation of measurement uncertainty for nitrided case depth with hardness method are emphasized in the study. The results show that measurement uncertainty of the whole nitrided case depth is significantly less than the effective nitrided case depth in the same test condition and method. The reason is that the uncertainty component introduced by test repeatability of measurement results is the main sources for the whole nitrided case depth measurement uncertainty; however, the main sources for the effective nitrided case depth measurement uncertainty are introduced by the boundary Vickers hardness values. The influence of indexing table and verticality deviation movement on the measurement results should be considered when evaluating measurement uncertainty for nitrided case depth with hardness method.