Erectile dysfunction (ED) is one of the major health concerns affects the quality of life among Thai male. The treatment of ED by the first-line drugs is limited to a certain group of patients due to their side effects and costs. Alternative medicine can be beneficial for the treatment of ED. This is a randomized, double-blind, placebo-controlled, crossover study aimed to assess the efficacy and safety of Cappra ® , a traditional herbal medicine which was used in Thailand for decades, for the treatment of mild and mild to moderate ED in Thai patients. A total of 63 patients with mild or mild to moderate ED were randomized to receive Cappra ® or placebo for two weeks in the first period, followed by one week washout period. The patients were switched to the alternative treatment in the second period. The efficacy was assessed by the International Index of Erectile Function (IIEF) questionnaire and adverse events. Sixty one patients completed the study. There was an improvement of IIEF score for all domains in Cappra ® group compared with placebo group. The mean change of IIEF score from baseline for erectile function domain of Cappra ® was significantly higher than placebo (4.87 vs 3.44, p = 0.032). The most common adverse events were dizziness (13.3% Cappra ® , 9.6% placebo), face numbness (1.6% Cappra ® , 0% placebo), and tachycardia (1.6% Cappra ® , 0% placebo). The results from this study demonstrated that Cappra ® is effective and welltolerated and can be used as alternative therapy for mild and mild to moderate ED.