Background: Thyme is a valuable medicinal plants that evaluation of its quality and quantity yield is necessary.

Objective: This study aimed to investigate the effect of salinity on morphological, physiological and phytochemical traits of thyme.

Methods: The study was carried out as a randomized complete block design at the Institute of Medicinal Plants with 4 levels of salinity treatments including (control, 50, 100 and 150 mM) and three replications. In this study some morphophysiologial and phytochemical traits of thyme were measured.

Results: Results showed the significant effect of salinity on plant height, number of lateral shoots, vegetative dry weight, root fresh weight, root dry weight, Length and Width of a Leaf. The results of the means comparison showed that by increasing levels of salinity, sodium content, electrolyte leakage and proline content increased conversely, the amount of potassium, relative water content, chlorophyll and carotenoid were decreased. The content of thymol and carvacrol increased by higher levels of salinity (100 mM sodium chloride) compared with control.

Conclusion: Although the majority of yield related traits negatively affected by salinity but the highest amount of thymol and carvacrol has been achieved in 100 mM NaCl.