This study has been conducted to evaluate the effects of torsional component of earthquake on seismic response of concrete arch dams. Ansys software based on finite element method was used for analysis and interaction effect is considered in models. Due to the geometry and behaviour of arch dams, a three-dimensional modelling was carried out in time domain and Newmark time integration scheme was developed to solve the time-discretized equations which are an unconditionally stable implicit method. The Morrow Point arch dam was selected as a case study for dynamic analysis. At first, the model was analysed due to El Centro earthquake for two cases of applying and no applying of torsional component of earthquake and the results are evaluated. Consider to obtained results, it is revealed that the torsional component of El centro earthquake can have the amplification effect on response of dam model. To show the effect of the frequency content of the torsional component and its power amplitude, the Taft earthquake was applied on the model. For this case, obtained results show that the responses are reduced due to applying torsional component. It can be concluded that the seismic response of arch dams could be increased or decreased, depending on the power amplitude and frequency content of the torsional component of earthquake. Finally, it should be mentioned that the effect of torsional component of earthquake must be considered with selecting of appropriate accelerograms for safety design of arch dams.