The present invention relates to polymorphic forms of 5-Azacytidine and the process for preparation thereof. The present invention further relates to Crystalline 5-azacytidine 5 designated as Form-SA-1 characterized by an X-ray powder diffraction pattern having at least four characteristic diffraction angle peaks at about 12.00, 12.60, 13.90, 15.15 and 31.40±0.20 2θ°, which is useful as active pharmaceutical ingredient in pharmaceutical compositions for the treatment of myelodysplastic syndrome.