Chrysanthemum is one of the ornamental plants that cultivated widely in worldwide. This flower is one of the most important cut and pot flowers in the world due to its high diversity of colors and shapes. The creation of mutation is an important method for the production of new cultivars, and many cultivars have been produced through spontaneous and induced mutations. In this study, explants of leaf pieces from three most cultivated chrysanthemum varieties were irradiated with different gamma rays. This experiment was conducted as factorial in randomized complete block design with three replications. The results showed that an appropriate dose of gamma ray to produce a mutation in the varieties used in this experiment, is 25 G-ray. The obtained results showed that the 25 G-ray in purple cultivar produced the greatest change in petal color with a mutation rate of 54.56%. Meanwhile, the maximum number of new colors belonged to the purple group. Also, in the pink cultivar, the highest number of colored flowers was observed with a change of 32.11% in the 25 G-ray treatment. Based on the results of this study, four new cultivars will be introduced to the Iranian flower industry as a new cultivar. Manuscript profile