Plant species with more than two sets of chromosome are called polyploids, which are usually spontaneously created by a mutation during the evolution process. The increased genetic diversity in polyploid plants is considered to be an important strategy in adapting them to new environments which are revolutionizing with time. The changes that are usually associated with auto and allopolyploids include alteration of cell size and morphological or physiological modifications. The aim of this study was to review some aspects of polyploidization and its impact on breeding of ornamental plants. Furthermore, the advantages and disadvantages of the polyploid plants, chromosome doubling agents and application of polyploidization in ornamental plants are reviewed and polyploidization as a modern breeding method is discussed. This review suggested that although there are some disadvantages with polyploid plants, however, they have major advantages over non-polyploids. In using chromosome doubling agents, results indicated that due to complexity of the mode of action of these agents and response of different plants to them, type and concentration of polyploid inducing agents, exposure period and explant type are to be optimized. Moreover, the results suggested that polyploidization induce changes in plant's vigor, size of the fruits and flowers, size and thickness of the leaves, fertility and resistance to biotic and abiotic stresses and therefore it is considered as a modern breeding method for ornamental plants.