Background: Selective IgA deficiency (SIgAD) is one of the most common primary antibody immunodeficiency diseases. The prevalence in Asia is lower than other areas. Asthma and allergic diseases are common among the SIgAD population. The aim of this study was to evaluate the prevalence of SIgAD among the adult asthmatic patients with variable immunoglobulin E (IgE) levels in serum. Patients and methods: 507 asthmatic patients of various age and sex who sequentially enrolled in the outpatient respiratory clinic were selected. Asthma diagnosis was based on the pulmonologist’s diagnostic and ATS criteria. IgA and total IgE levels in serum were measured according to manufacturer’s recommended kits. Results: 64 (13%) subjects detected as SIgAD. Mean age recorded 34.5 ± 13.9 SD years. The patient included 57% male and 43% female, respectively. Allergic asthma recorded 40% (205) of the study population. Conclusion: The SIgAD was remarkably found among Iranian adults with asthma. However, its frequency was lower in allergic asthma in comparison to the non-allergic subset. Additionally, the number of SIgAD subjects declined with increasing age. Detection of SIgAD among the asthmatic population may be effective in reducing complications.