Combination therapy is required for the treatment of moderate acne vulgaris. However, patient compliance in applying multiple topical formulations is poor. To assess the efficacy and safety of a fixed-dose combination gel with adapalene 0.1% and clindamycin 1% (adapalene-clindamycin) relative to adapalene 0.1% monotherapy and clindamycin 1% monotherapy in patients with moderate facial acne vulgaris. This was a randomized, controlled, assessor-blind, phaseIII study conducted in patients with moderate facial acne vulgaris. A total of 1617 patients were enrolled. At week12, patients in the adapalene-clindamycin gel treatment group showed a significant reduction in the percentage change from baseline in total lesion count (- 66.85%), compared with adapalene alone (- 50.82%) or clindamycin gel alone (- 57.61%). The difference in the least square means of the adapalene-clindamycin gel group and adapalene group, or clindamycin gel group was - 16.08% (95%CI - 19.95% to - 12.21%) and - 9.38% (95%CI - 13.25% to - 5.51%;), respectively. At week12, 19.28% of participants who received adapalene-clindamycin gel achieved at least 2-grade improvement in IGA, versus 7.74% with adapalene gel (OR 3.05, 95%CI 1.93, 4.80) and 14.77% with clindamycin gel (OR 1.42, 95%CI 0.97, 2.07). The study also achieved all its secondary endpoints. Adverse event rates were mostly mild to moderate and comparable across the three treatment groups. Adapalene 0.1%-clindamycin 1% combination gel is well tolerated and demonstrated superior efficacy over 0.1% adapalene gel monotherapy and 1% clindamycin gel monotherapy for the treatment of moderate acne vulgaris. ClinicalTrials.gov identifier NCT03615768.