Cumin is one of the most agriculturally valuable plants, in the semi-arid tropical regions of Iran. In this research, drought tolerance of 49 cumin ecotypes were evaluated under irrigated, and rained conditions in the field during two years (2010 and 2011). Five drought tolerance/susceptibility indices including mean productivity (MP), geometric mean productivity (GMP), stress tolerance index (STI), tolerance (TOL) and susceptible stress index (SSI) were applied. Results of combined analysis based on the experiments showed a significant variation among ecotypes for grain yield and, it was decreased due to drought stress. The mean grain yield of Ardestan and Ravar in normal and drought stress conditions possessed the highest values respectively. According to the results derived from principal component analysis, bi-plot display and STS equation, Ravar was identified as the most drought tolerant ecotype. In conclusion, this suitable ecotype could be recommended for cropping in regions with limited water resources, also MP, GMP and STI indices were found to be more effective in identifying drought-tolerant and high yielding ecotypes in both conditions.