Background: The importance of sleep in physical and mental well-being is generally acknowledged by both health professionals and the general public.This study investigated the effects on inhalation aromatherapy on sleep quality in cardiac patients.Methods: Ninety-six men and women aged between 20 and 75 were randomized to inhale aromatherapy essential oil from Lemon Balm (Melissa officinalis L.) or odorless sesame oil (the placebo) for 30 minutes twice daily for 3 days. Sleep quality by Verran Synder- Halpern (VSH) scale were assessed before and after period.Results: Compared with the placebo, the experimental group showed that the components such as subjective sleep quality, sleep disturbance, and daytime dysfunction were significantly decreased (P< 0.005).Conclusion: Aromatherapy may be used as an independent nursing intervention for improving sleep quality of cardiac patients.