Acne vulgaris, an inflammatory skin disease with different clinical appearances, is a common problem in most adolescents. It seems that using combinations of topical agents can decrease resistance to the treatment and improve the efficacy. Therefore, we evaluated the effects of azelaic acid (AA) 5% and clindamycin (Clin) 2% combination (AA-Clin) on mild-to-moderate acne vulgaris. The efficacy and safety of 12-week treatment with AA-Clin in patients with mild-to-moderate facial acne vulgaris were evaluated by a multicenter, randomized, and double-blind study. A total of 88 male and 62 female patients were randomly assigned to one of these treatments: AA 5%, Clin 2%, and combination of them. Every 4 weeks, total inflammatory and noninflammatory lesions were counted, acne severity index (ASI) was calculated, and patient satisfaction was recorded. Treatment for 12 weeks with combination gel significantly reduced the total lesion number compared with baseline (p < 0.01), as well as Clin 2% or AA 5% treatment groups (p < 0.05 or p < 0.01). The percentage of reduction in ASI in combination treated group (64.16 ± 6.01) was significantly more than those in the Clin 2% (47.73 ± 6.62, p < 0.05) and 5% AA (32.46 ± 5.27, p < 0.01) groups after 12 weeks. Among the patients in the AA-Clin group, 75.86% of males were satisfied or very satisfied and 85.71% of females were satisfied or very satisfied. This trend was significant in comparison to the number of patients who were satisfied with AA 5% or Clin 2% treatment (p < 0.01). Seven patients in AA-Clin group (incidence = 22%) showed adverse effects that were not statistically significant compared to treatment with individual active ingredients. The profound reduction in lesion count and ASI by combination therapy with AA-Clin gel in comparison to individual treatment with 5% AA or Clin 2% suggested the combination formula as an effective alternative in treatment of acne vulgaris.