Introduction and purpose: Air pollution is an important risk factor for the environment and public health, associated with increased severity of respiratory diseases. This study aimed to evaluate the association between various air pollutants and number of cases with severe acute respiratory syndrome referred to emergency medical centers in Tehran, Iran in 2013. Methods: In this ecological study, the relationship between air pollution and acute respiratory symptoms in patients referred to the emergency centers of Tehran in 2013 was assessed. In total, 36787 patients with acute respiratory symptoms has been registered in these centers. Data on the number of cases with acute respiratory symptoms and air pollutants of emergency centers and air quality monitoring stations were collected. Moreover, Poisson regression was used to assess the relationship between air pollutant concentrations (PM_2.5, SO₂, NO₂, O₃, CO) and the number of cases with severe acute respiratory syndrome. Results: The results of the current study demonstrated that CO (weekly average IRR=1.1) and SO₂ (three days average IRR=1.03 and weekly average IRR= 1.04) increased the risk of respiratory diseases 10%, 3%, and 4%, respectively. Consequently, longer duration of pollutants would increase the risk of respiratory syndromes. Conclusion: According to the results of this study, increased air pollutant concentrations could be associated with escalated number of patients with acute respiratory symptoms referred to the emergency medical centers in Tehran.