This paper compares the analysis of a Roller Compacted Concrete (RCC) dam with and without galleries under seismic loading. The effects of different sizes and shapes (circle, octagon and square) of gallery have also seen in the analysis. For this purpose, twodimensional (2D) Finite Element Model (FEM) is used for nonlinear dynamic analysis by means of finite element software, ABAQUS. In addition, Concrete Damaged Plasticity (CDP) model is also implemented to inspect the tensile damage of the dam during earthquake excitation. Kinta RCC dam of Malaysia is considered as a case study in analysis. From the seismic analysis, it was found that by increasing the size of openings, stress is developed around the galleries. As a result, the gallery with circle shape is more appropriate for the dam in comparison to gallery with square and octagon shapes. From crack propagation analysis and displacement response, it was also found that the gallery with circle shape behaves better than the gallery with square and octagon shaped.