BACKGROUND: The present study was a randomized, double-blind, placebo-controlled, multi-center trial to evaluate the efficacy and safety of prolonged-release melatonin (PRM) in Parkinson's disease (PD) patients with poor sleep quality. METHODS: PD patients with a global Pittsburgh Sleep Quality Index (PSQI) score > 5 were included. Patients were assessed using the PSQI, a rapid eye movement sleep behavior disorder screening questionnaire, the Epworth Sleepiness Scale, Non-Motor Symptoms Scale (NMSS), Parkinson's Disease Quality of Life-39 (PDQ-39), and Unified Parkinson's Disease Rating Scale (UPDRS)-III at the beginning of the study and after 4 weeks of treatment with 2 mg of PRM. Partial correlation analysis was performed to investigate the relationship between PSQI score and the other scales. RESULTS: Thirty-four PD patients with poor sleep quality were enrolled and divided into 2 groups based on medication; PRM (n = 16) and placebo (n = 18). Regarding efficacy, PSQI was significantly improved in the PRM group compared to the control group. Improvement in the NMSS and PDQ-39 summary index were observed in the PRM but not in the placebo group; UPDRS-III score was not significantly changed in either group. PSQI improvement correlated with improvement in NMSS score and PDQ-39 summary index. Regarding safety, all enrolled subjects did not complain of side effects due to PRM. CONCLUSION: PRM is an effective and safe treatment option for subjective sleep quality in PD patients and beneficial effects on sleep quality are associated with improved non-motor symptoms and quality of life in PD patients.