Base isolated buildings perform better than non-isolated building when subjected to strong earthquake. Earthquakes are unpredictable and it can hit the building from any direction. Hence this research aims to study the effect of incidence angle of ground motion on the isolated building. For this an isolated and a non-isolated model were developed by using SAP2000. The ground was applied in both the horizontal directions X and Y simultaneously with incidence angle 0°, 30°, 45°, 60° and 90° with the principal axes of the buildings. Base shear, inter-storey drift and storey displacement responses in terms of both models’ non-linear time history analyses with four load cases have been compared. In this study it was found that the effect of incidence angle of ground motion was not the same for isolated and non-isolated building. If the critical angle is the angle at which a response’s resultant is at its greatest, then the critical incidence angle for a non-isolated model was found to 60°, whereas the critical incidence angle for an isolated model was 45° for the particular case.