Low-energy ultrasound shows multiple physiological effects on plant cells and tissues, and has numerous applications in plant biotechnology, especially in elicitation of secondary metabolites production. In this research, the effects of ultrasound on Iranian poppy cell suspension culture were investigated. For this purpose, cell suspension cultures were treated with ultrasound and then, cell viability and growth, activity of some antioxidant enzymes and amount of total protein, hydrogen peroxide, proline and thebaine were measured. The results showed that viability and dry weight (growth) of cells were significantly decreased under ultrasound treatment. In addition, increase in time after treatment led to severe reduction in cell viability and growth. Amount of proline and total protein were increased under ultrasound treatment, compared to the control. Analysis of variance revealed that hydrogen peroxide content of cells and activity of catalase, peroxidase and superoxide dismutase enzymes were significantly influenced by ultrasound, time after treatment and their interaction. So that, ultrasound treatment led to increased content of hydrogen peroxide and also elevated activity of aforementioned antioxidant enzyme in comparison to the control cells. Thebaine production in cells was significantly increased on 48 hours after treatment with ultrasound, compared to that of the control cells.