Catharanthus roseus (L.) G. Don is valuable medicinal plant grown as an ornamental plant. The study was carried out at Gulf Coast Research and Education Center, University of Florida, USA. to evaluate the morphological and anatomical changes from induced polyploidy in periwinkle for this purpose colchicine was applied at four different concentrations 0.0, 0.05, 0.1 and 0.2% for seedling treatment. The results showed that raising colchicine doses caused an increasing of survival percentage and tetraploid plants number. Polyploids showed an increment in leaf thickness, stomatal size, pollen diameter and pollen viability compared to diploid plants. Flow cytometry verified the existence of tetraploids and mixoploids from various colchicine-treated plants especially 0.2 which was found efficient on inducing polyploidy in the plants followed by 0.1% as compared to other concentration under study.