Zagros Orogeny System resulted due to collision of the Arabian with Eurasia. The region has the ocean-continent subduction and continent-continent collision; and convergence velocity shows variation from east to west. Therefore, this region shows the complex tectonic stress and a wide range of diffuse or localized deformation between both plates. The in-situ stress and GPS data are very limited in this region, therefore, we performed a numerical simulation of the stresses causing deformation in the Zagros-Iran region. The deviatoric stresses resulting from the variations in lithospheric density and thickness; and those from shear tractions at the base of lithosphere due to mantle convection were computed using thin-sheet approximation. Surface observations of strain rates, SHmax, plate velocities etc. are explained using the joint models of lithosphere and mantle, suggesting a good coupling between lithosphere and mantle in most parts of Zagros and Iran. However, the deformation in east of Iran is caused primarily by lithospheric stresses. Plate motion of Arabian plate is found to vary along the Zagros belt from north-northeast in south-east of Zagros, north in central Zagros to slight northwest in northwestern Zagros. The output of this study can be used in seismic hazards estimations.