Fretting fatigue is an important consideration in the design and optimization of mechanical systems and assemblies in the recent times. Empirical approaches, multi-axial fatigue considerations and fracture mechanics approaches are considered for assessing fretting fatigue damages at contact interfaces of assemblies. Ruiz criteria is an effective empirical approach for evaluation of Fretting Fatigue Damage Parameter (FFDP) and has been demonstrated in two dimensional fretting studies of a typical dovetail interface problem. The current paper considers the extension of Ruiz criterion for assessing fretting fatigue damage parameter for three dimensional problems. Two approaches viz. summation of FFDP computed independently along the two slip directions and combined maximum principal-shear stress approach have been proposed for the FFDP evaluation, considering three dimensional stress and slip components over contact interface. FFDP evaluation using maximum principal-shear stress approach is observed to be more appropriate for three dimensional problems. © 2013 The Authors.