Phalaris is a grass which is distributed throughout the temperate regions of the world. There are many taxonomic problems in this genus. In order to clarify the taxonomy and the interrelationships among Iranian Phalaris taxa, including Ph. minor, Ph. arundinaceae, Ph. brachystachys and Ph. paradoxa 70 qualitative and quantitative morphological characteristics were examined. Numerical taxonomy was performed on 36 accessions of 5 taxa, concerning intra- and inter-populations variations as well as inter-specific relationships. The most variable morphological characters in the species delimitation were also determined. The species differed significantly in most of chosen qualitative characters. Results show a clear similarity between two varieties of Ph. paradoxa. Despite the wide range of habitats where the accessions were gathered, they showed four definite spots in their PCA ordination graphs. This showed the efficiency of chosen morphological characters in this study. An identification key based on studied features was provided and the species relationships were discussed.