Introduction/Aim: The use of macronutrient and micronutrient foods is associated with the duration of sleep. This study aimed to determine the effect of zinc supplements on the sleep quality of older adults. Methods: The current parallel randomized clinical trial study was performed using a convenience sampling method. One hundred and fifty older adults who met the inclusion criteria were assigned to intervention and control group. The participants in the intervention group received a daily dose of 30 mg zinc supplementation pill for 70 days and the control group did not receive any supplement. Sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI). Serum zinc level in both groups was measured through the auto-analysis method. The questionnaire was completed and the serum level of zinc was measured twice, before the intervention and 70 days after the intervention. Results: Both groups were homogeneous in terms of demographic variables, sleep quality, and serum zinc level before the intervention. Of all, 73.3% of older adults in the intervention group and 74.7% of older adults in the control group had poor sleep quality. Sleep quality in the intervention group, as compared with the control group, significantly improved after the intervention. Furthermore, serum zinc levels in older adults in the intervention group, as compared with the control group, significantly increased after the intervention. Conclusion: Based on the results of this study, it is recommended to utilize zinc supplementation as a new therapeutic approach for improving sleep quality in older adults.