OBJECTIVE: To assess the effect of valerian root extract on the sleep quality of patients after coronary artery bypass graft (CABG) surgery. METHODS: The patients who participated in this triple-blind clinical trial were selected by permuted block randomization. The participants were assigned to the valerian (n=36) and placebo (n=36) groups. The valerian group received 530 mg of valerian capsules for 30 nights after CABG surgery, and the placebo group received 530 mg of the placebo capsules containing wheat flour. The Pittsburgh Sleep Quality Index (PSQI), the prothrombin time (PT) and partial thromboplastin time (PTT) were assessed on four occasions, including the baseline, the 3rd, 14th and 30th days following intervention. RESULTS: The odds ratio of worsened sleep quality significantly varied over time (the interaction of time and group) in the valerian group compared to the placebo group in various dimensions including total sleep quality (P=0.001), sleep latency (P<0.01), sleep duration (P=0.020), sleep efficiency (P=0.001) and daytime dysfunction (P=0.025). No significant difference was observed in the alterations of the odds ratio of PT in the two groups over time. (P=0.371). CONCLUSION The consumption of oral valerian root extract over 30 nights could significantly improve the patients' sleep quality safely after CABG surgery.