In the Framework of identifying defects in structures, Damage Index Method (DIM) is considered one of the trustable tools used intensively. In the present research, DIM – modal displacement based - was applied on experimental data to detect damage for masonry piers. Damage index (DI) was obtained by comparing modal displacement functions for damaged and sound conditions. Firstly, two scaled down piers were prepared experimentally for examination. The piers were of same unit area while the thicknesses were 170, and 260 mm, respectively. The physical models were subjected to different artificial crack patterns. The cracks were created for each pier on three steps representing different intensity of damage. The piers were then examined under free vibration mode at sound condition and after each degradation. The collected records were processed, and DIM was applied. Furthermore, parametric numerical analysis was used to study the effect of crack dimensions, location, shape, and repetition among the simulated piers. The results showed that the selected DI was effective in detecting cracks in masonry structures for all examined cases. Moreover, the investigation showed that as the severity of cracks increased, the identification of damage became easier and was reflected in an increase in DI value. DIM was also able to detect expected route of cracks. On the other hand, DIM can't be used to obtain degradation level directly but for comparison between severity of cracks in different stages of damage.