Although Rosa damascena , a national flower of Iran, is economically important aromatic plant its growth and development has been limited by drought stress. Nano-silicon (nSiO 2 ) is an efficient approach to mitigate the deleterious impacts of stress on field crops. To investigate the effect of nSiO 2 (0, 50 and 100 mg L -1 ) in simulated drought stress by polyethylene glycol (PEG) (0, 50, 75 and 100 g L -1 ) invitro culture on quality of Rosa damascena Kashan genotype, an experiment was conducted as a completely randomized design. As increasing in drought level, leaf chlorophyll, area and number, shoot fresh/dry weight, biomass and shoot height decreased while electrolyte leakage percentage and proline content increased. However application of 100 mg L -1 nSiO 2 prevented the reduction or increase of the mentioned traits. The highest proline content related to the explants in 100 g L -1 PEG without nSiO 2 while control explants treated with 100 mg L -1 nSiO 2 had the lowest proline content. The positive effect of nSiO 2 was confirmed also in control plants as they had the highest leaf number and leaf area, as well as the strongest membrane stability. Total phenol, flavonoid as well as DPPH radical scavenging activity of the leaves were increased at severe water deficit and it was also intensified by ‎ nSiO 2 application. Kashan genotype treated with 75 g L -1 PEG and 100 mg L -1 nSiO 2 likely had the same performance with the level of 50 g L -1 PEG without nSiO 2 which is indicating the tolerance threshold of the plant to drought.