The present invention relates to a process for preparation of crystalline non-needle shaped Form-SA of Imatinib mesylate (I). The invention also relates to crystalline Form-SA obtained by the process of the present invention, the said Form-SA being substantially pure, stable, non-needle shaped and characterized by X-ray powder diffraction pattern comprising of at least five 2&thetas° peaks selected from 10.67, 12.90, 15.34, 19.49, 19.80, 26.06, 26.32 and 28.89±0.05 2&thetas°. The invention further relates to pharmaceutical compositions comprising non-needle shaped crystalline Form-SA of Imatinib mesylate, useful for the treatment of cancer.
