Objective The aim of this study was to examine whether melatonin is involved in the pathogenesis of nasal polyposis. Method This study included 29 patients with nasal polyposis and undergoing functional endoscopic sinus surgery. As a control group, 26 patients who had been operated on for a deviated nasal septum and concha bullosa were enrolled. Samples were taken from the nasal polyp tissue and from the resected middle concha bullosa mucosa of the control group. Serum samples were taken from all patients. Results It was found that the tissue and serum melatonin levels in the nasal polyp group were significantly lower compared with the tissue and serum melatonin levels in the control group. Conclusion In nasal polyposis, the melatonin level in the serum and tissue is lower than in individuals without polyposis. This deficiency may play a role in the pathogenesis of nasal polyposis.