Objective: As the exact etiology of recurrent aphthous stomatitis remains unknown, its treatment has primarily been palliative to relieve the pain, associated inflammation, and duration of the lesions by using antibacterial mouthrinses, analgesics, and immunomodulators. Nevertheless, no treatment has been universally effective in management of recurrent aphthous stomatitis, which necessitates the search for novel therapeutic agents. The aim of this study was to assess the clinical efficacy of the aqueous extract of Rosa damascena, which has reported anti-inflammatory and antinociceptive properties, in the treatment of recurrent aphthous stomatitis. Method and Materials: This was a randomized, double-blind, placebo-controlled investigation. Fifty patients were enrolled in this 2-week study; the clinical efficacy of the mouthwash on pain, size, and number of ulcers in the test group was compared with that of the placebo group on days 4, 7, 11, and 14. Results: There were no statistically significant differences between baseline parameters. However, statistical analysis indicated a significant difference on days 4 and 7 between the placebo and test groups for all parameters. Conclusion: This study showed that mouthwash containing Rosa damascena extract was more effective than the placebo in the treatment of recurrent aphthous stomatitis. Keywords: clinical trial, placebo, recurrent aphthous stomatitis, Rosa damascena