- Background: Anticytokine autoantibodies (AAbs) involve a great panel of cytokines both in healthy subjects and in patients with various diseases, but their incidence and pathophysiologic role are widely debated. The issue of AAbs in chronic rhinosinusitis (CRS) has never been explored. Objective: The aim of the study was to check AAbs in patients with CRS and with nasal polyps (CRSwNP) and patients with CRS and without nasal polyps (CRSsNP). Methods: One-hundred subjects with CRS and 40 healthy controls were included. CRS severity was determined by the 22-item Sino-Nasal Outcome Test and Lund-Mackay scores. Levels of immunoglobulin A (IgA), secretory IgA, IgG, IgE, interleukin (IL) 1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, and IL-17A, and AAbs levels in subjects' serum and nasal secretions (NS) were measured by the enzyme-linked immunosorbent assay. Results: Forty-six patients with CRSsNP, 25 women (54.3%) and 21 men (45.7%), mean (standard deviation [SD]) ages 34.1 ± 12.3 years; and 54 patients with CRSwNP, 24 women (44.4%) and 30 men (55.6%), mean (SD) ages 37.9 ± 17.5 years. A group of 40 healthy subjects served as controls. In both CRSsNP and CRSwNP groups, serum and NS IL-1β, IL-4, IL-5, IL-6, IL-8, IL-10, and IL-17A levels were higher compared with healthy controls, but there was no difference in the serum levels of cytokines between the CRSsNP and CRSwNP groups. Binding IgA antibodies against IL-1β, IL-2, IL-5, and IL-8 were found at low levels in NS of both patients with CRSsNP and patients with CRSwNP. The highest levels of AAbs were detected against IL-5 (0.43 ± 0.38 optical density values) and IL-17A (0.51 ± 0.32 optical density values) in NS of patients with CRSwNP. In the CRSwNP group, a positive correlation was found between NS IL-5 and anti-IL-5 AAbs (r = 545; p < 0.001). Positive correlations between anti-IL-5 AAbs with NS total IgE (r = 0.424; p = 0.001) and with NS secretory IgA (r = 0.545; p < 0.001) were noted in the CRSwNP group. Conclusions: In patients with CRS, IgA class AAbs were detected in NS, whereas the highest levels of anti-IL-5 and anti-IL-17A AAbs were detected in patients with CRSwNP. Maybe these AAbs indicate disruption of immune tolerance and mucosal autoimmunity.