Twenty-six selected genotypes of Phalaris aquatica L. from Iranian germplasm were evaluated to evaluate the genetic diversity of some agromorphological characteristics. Each selected genotype was cloned and planted as spaced single plants according to a randomized complete block design (RCBD) with four replications in 2016 and 2017. Large and significant (p < 0.01) differences among genotypes were found for all traits. The estimates of broad sense heritability were low to high (hb 2 = 0.16 – 0.75) for studied traits. High heritability estimates for dry matter yield (DMY) indicate a sufficient genetic variability for further improvement. There was the highest heritability rate and genetic advance for plant height and DMY. Selection for traits with high heritability and genetic advance can be successful. The dry matter yield cut 1 (DMY1) correlation with the number of days to flowering, number of days to pollination, plant height, and crown diameter cut 2 was positive and significant. In stepwise multiple linear regression, the plant height, number of stems per plant, and spike length explained more than 84% of the total variation of DMY1. The plant height was the most crucial component of DMY1. The path analysis showed that plant height positively affected DMY1 (0.83). The highest negative indirect effects on DMY1 were observed for plant height via the number of stems per plant (–0.238). Axes 1 and 2 of the principal coordinate analysis explained 40.94% and 18.48% of the variation, respectively, and, although not entirely separated, general groupings can be determined. In factor analysis, component 1 was positively associated with the traits dry matter yield cut 2 (DMY2) (0.855), dry matter yield (0.821), and plant height (0.755). Therefore, the first component can be called the biomass component. Finally, selection would be more effective in improving forage yield based on yield components. In conclusion, the results indicated appropriate genetic variability in the
