Ulmus Ulmaceae (UU) is a bushy plant in Iran, which the plant has been applied as an ethnomedicinal plant in Iranian traditional medicine. In comparison to many other plants, there is a very little data about antibacterial properties of UU aqueous extract collected from Iran. In this work, effect of aqueous extract of UU on growth of Staphylococcus aureus ATCC No. 25923 (SA) in macro-dilution Mueller-Hinton broth, agar disk and agar well diffusion is indicated. MIC and MBC values were 0.125 and 0.5 g/ml concentration, respectively. By increasing the concentration of the UU extract, the inhibition zones increased. The present research shows the antibacterial effects of the medical plant on SA, suggesting to use as an antibacterial agent. Extraction of active molecules will be the future work to peruse.