The aim of this research was to determine the responses of diploid and tetraploid Italian ryegrass cultivars to interactive effects of salinity and temperature during the germination period. The seeds of diploid (cv Efe) (2×) and tetraploid (cv Baquena) (4×) Italian ryegrass were used as materials. All data obtained in the study were subjected to analysis of variance in accordance with the completely randomized design as triplicate using a three-way factorial ANOVA. Therefore, using multivariate analysis at different temperatures, provided information about the relative importance of each trait. The seeds were germinated at three different temperatures (15ºC, 25ºC, 35ºC) with 12-h photoperiod to screen and evaluate the effects of three different sodium chloride concentrations (NaCl) (0, 75, 150 mM) on the seed germination process of the Italian ryegrass cultivars. Germination energy (%) and germination percentage (%), root length (cm), shoot length (cm), fresh weight (g), dry weight (g), promptness index, and simple vigour index were measured to define germination responses. At different temperatures and salinity conditions; tetraploid Italian ryegrass had a better performance as compared to diploid Italian ryegrass. 25ºC (T_opt) and 75 mM (S₂) are the optimal temperature and salt level for both cultivars during the germination process.