Background: Melatonin is a hormone that regulates the sleep-wake cycle and has immunomodulatory and anti-inflammatory roles. Aims: The aim of this study is to assess melatonin levels and investigate the association with pruritus severity, sleep quality, and depressive symptoms in dermatoses with nocturnal pruritus. Methods: The study was a prospective study with 82 participants, including 41 patients and 41 healthy volunteers. The visual analog scale (VAS), Pittsburg Sleep Quality Index (PSQI), and Beck Depression Inventory (BDI) were recorded for each patient. To assess the melatonin levels, urinary 6-sulfatoxymelatonin levels in the first urine in the morning were measured. Results: Melatonin concentrations were significantly lower (P = 0.007), while the BDI (P = 0.001) and PSQI (P = 0.001) scores were significantly higher in the patients with pruritus than in the healthy control subjects. There was an inverse correlation between melatonin levels and PSQI scores (r = -0.355, P = 0.023), and a positive correlation was detected between BDI scores and PSQI scores (r = 0.631, P = 0.001) in the pruritus group. Conclusion: Melatonin levels were found to decrease in relation to sleep quality in nocturnal pruritus patients. Low melatonin levels in these patients may be associated with sleep disorders and pruritus.