Objective: Sleep disturbances are commonly experienced by hospitalized patients due to environmental factors, underlying medical conditions, and anxiety, which may negatively affect the recovery process. Nature sound music therapy is a non-pharmacological intervention that may improve sleep quality. This study aimed to determine the effect of nature sound music therapy on the sleep quality of patients admitted to the inpatient wards of Manado Adventist Hospital. Methods: This quantitative study employed a pre-experimental, one-group pre-test and post-test design. A total of 34 participants were recruited using purposive sampling. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI). The intervention was administered before bedtime for three consecutive days. Data were analyzed using the Wilcoxon signed-rank test. Results: Before the intervention, most participants had poor sleep quality (76.5%), while only 23.5% had good sleep quality. After the intervention, sleep quality improved, with 76.5% of participants reporting good sleep quality and 23.5% remaining poor sleepers. Nature sound music therapy had a statistically significant effect on the sleep quality of hospitalized patients (p < 0.001). Conclusion: Nature sound music therapy has the potential to serve as a simple, safe, and cost-effective non-pharmacological nursing intervention for improving patients’ sleep quality. Further studies should employ a control group, a larger sample size, and a longer intervention period to strengthen the evidence regarding its effectiveness. Â