Despite extensive use and cultivation of "Tareh Irani" the native vegetable of Iran, there has been few research works carried out on it, specially regarding its drought tolerance. This research was conducted to study the effects of five drought levels (30, 50, 80, 200 and 500 kPa) on yield and some morphological as well as physiological characteristics of two Tareh Irani populations (Hamedani and Shadegani), employing a factorial experiment of completely randomized design. The drought stresses were applied following the 2nd cut of plants. The results revealed that drought stress exerted significant effects on all the characteristics but effects of population cultivars and their and its interaction effects with drought stress were not significant. By increase in the level of drought stress, yield, leaf number, leaf area, dry matter percentage, chlorophyll contents of leaves, relative water content and water potential of leaves decreased but the ratio of root fresh weight to leaf fresh weight and as well the number of stomata increased. The results were similar for different cuts. In comparison with control (30 kPa) the yield in 50, 80, 200 and 500 kPa drought treatments decreased by 14, 46, 75 and 82 percent, respectively. The results were observed to be similar for other quantitative traits. Finally, taking into account the potential of Tareh Irani for keeping its relative water content and as well its water potential of leaves in favorable levels in face of high levels of drought stress, this plant can be considered as a tolerant plant to drought stress, but on the other hand a high decrease in yield and in some other quantitative traits of this vegetable in moderate to high levels of drought stress, can lead to its being classified as a sensitive crop to drought stress.