Fatigue life of automotive engine mount insulator made of natural rubber was evaluated. In order to develop an appropriate fatigue damage parameter of the rubber material, a series of displacement controlled fatigue tests was conducted using 3-dimensional dumbbell specimens with different levels of mean displacement. It was shown that the maximum Green-Lagrange strain was a proper damage parameter, taking the mean displacement effects into account. Nonlinear finite element analyses of the rubber engine mount insulator and 3D dumbbell specimen were performed based on a hyper-elastic material model determined from the simple and equi-biaxial tension tests. Fatigue life prediction of the engine mount insulator was made by incorporating the maximum Green-Lagrange strain values, which was evaluated from the finite element analysis and fatigue tests, respectively. Predicted fatigue lives of the engine mount insulator showed a fairly good agreement with the experimental fatigue lives.