PURPOSE: The purpose of this study was to investigate the effects of aromatherapy on sleep quality. METHODS: This is a systematic review of randomized controlled trial studies (PROSPERO registration number CRD42017064519). In this study, the PICO were adults and the elderly, aromatherapy intervention, a comparative intervention with the control and placebo oil groups, and sleep. The selected articles were in English, Korean, and Chinese. RESULTS: The results of the meta-analysis showed that the effect sizes of the experimental group were 1.03 (n=763, SMD=1.03, 95% CI 0.66 to 1.39) (Z=5.47, <.001). In the aromatherapy intervention group, the effect size of sleep was statistically significant (Q=9.39, df=2, =.009), with a difference of 0.77 for inhalation, 1.12 for oral intake and 2.05 for massage. A post-analysis showed that the effect of massage on sleep was significantly greater than the inhalation method. The regression coefficient of the intervention period, B=0.01 (Z=1.43, =.154), also showed that the longer the intervention period, the larger the effect size; however, it was not statistically significant. CONCLUSION: A total of 23 literature analyses showed that aromatherapy is effective in improving quality of sleep, and the massage method is more effective in improving quality of sleep than the inhalation method. A meta-ANOVA showed that the aromatherapy intervention affected the high heterogeneity of the effect size. Thus, future research with stricter control in methods and experimental procedures is necessary.