Salinity limits the oat germination and seedling growth at early growth stages. This study was aimed to determine the morpho-physiological response of 33 (10 commercial and 23 landraces) oat genotypes to four NaCl salinity stresses (0, 30, 60 and 90 mM) under in vitro conditions during seed germination and early seedling stages. The effect of NaCl stress on water uptake, germination ratio, root length, shoot length, root fresh weight, root dry weight, shoot fresh weight, shoot dry weight, ion contents (Na+, K+, Ca and K+/Na+) for both root and shoot and photosynthetic pigments (Chl a, Chl b, Chl a + b and carotenoid) in 33 oat genotypes was investigated in the experiment. The investigated traits were decreased by salt stress from control (0 mM) to 90 mM doses including 18% for water uptake, 54.9% for germination rate, 87.5% for root length, 87% for shoot length, 74.5% for root fresh weight, 38.5% for root dry weight, 79.1% for shoot fresh weight, 62.4% for shoot dry weight, 84.5% for root K+/Na+, 97% for shoot K+/Na+, 62.2% for chl a, 51.6% for chl b and 61.7% for carotenoid. It was found that the oat genotypes showed a wide variation in the cluster analysis based on morpho-physiological traits. According to the principal component biplot analysis, principal components (PC1 and PC2) represented (33.9 and 16.4%, respectively) 50.3% of the total variation among the genotypes under salt stress. TL582 landrace showed greater performance for the investigated traits among oat genotypes for the highest salt tolerance. The investigated traits are important growth indices and physiological parameters to be used as selection criteria to evaluate salt tolerance in oat genotypes. The results of the study determined the registered and local genotypes that can be used as parent lines in breeding programs.