<b><i>Introduction:</i></b> Primary immunodeficiencies are a heterogeneous group of diseases associated with an increased incidence of infections, autoimmunity, autoinflammatory diseases, allergies, and cancer. Rhinosinusitis is one of the most common infections in these patients. In our study, we aimed to determine the presence of chronic rhinosinusitis in our patients with primary immunodeficiency and to investigate the etiology of chronic rhinosinusitis. <b><i>Methods:</i></b> Forty-four patients (age range: 4–26 years) diagnosed with primary immunodeficiency were enrolled in our study. Patients were interviewed about the symptoms of chronic rhinosinusitis, and nasal endoscopic examinations were performed prospectively. The results of laboratory tests, medications, skin allergy tests, and the patients’ lung computed tomography were retrospectively recorded from patient files. <b><i>Results:</i></b> The distribution of patients’ diagnoses included 38.6% (<i>n</i> = 17) primary antibody deficiencies, 6.6% (<i>n</i> = 3) combined immunodeficiencies, 27.3% (<i>n</i> = 12) combined immunodeficiencies with syndromic features, 6.8% (<i>n</i> = 3) phagocytic disorders, and 20.5% (<i>n</i> = 9) immune dysregulation disorders. There was no significant difference in the frequency of chronic rhinosinusitis among the different immunodeficiency groups. There were no significant differences between chronic rhinosinusitis and conditions such as atopy, hypogammaglobulinemia, and treatments with immunoglobulin and/or azithromycin. The incidence of chronic rhinosinusitis was 77.8% (<i>n</i> = 7) in patients with a history of acute sinusitis and 20% (<i>n</i> = 7) in patients without a history of sinusitis, with a statistically significant difference between them (<i>p</i> = 0.002). <b><i>Conclusion:</i></b> Chronic rhinosinusitis is more common in patients with primary immunodeficiencies than in the normal population. For effective treatment, it is necessary to identify the factors that cause chronic rhinosinusitis. Further studies involving larger patient populations are needed to explain the mechanisms of chronic rhinosinusitis.