Importance: Most patients with tuberous sclerosis complex (TSC), an autosomal-dominant disorder that is caused by the constitutive activation of mammalian target of rapamycin, experience disfigurement caused by skin lesions involving facial angiofibromas. Many have been left untreated because of a lack of therapeutic options that are less invasive than surgery or laser treatment. Objective: To confirm the efficacy and safety of sirolimus gel, 0.2%, for treatment of patients with angiofibromas and/or skin lesions. Design, Setting, and Patients: Multicenter, randomized clinical trial at 9 centers in Japan from December 2015 to October 2016 including 62 children and adults with TSC. Interventions: Patients who developed angiofibromas were randomly assigned, in a 1:1 ratio, to receive sirolimus gel, 0.2%, or placebo, each applied topically twice daily for 12 weeks. Main Outcomes and Measures: The primary end point was composite improvement in the size and color of angiofibromas in photographs at week 12 of treatment. It was assessed by an independent review committee comprising 3 blinded dermatologists who categorized patient results into the following 6 categories: "markedly improved," "improved," "slightly improved," "unchanged," "slightly aggravated," and "aggravated." Results: Sixty-two patients (27 pediatric and 35 adult; 34 [55%] female; mean [SD] age, 22.5 [11.9] years) were enrolled and randomly assigned to receive sirolimus gel, 0.2% (30 patients), or placebo (32 patients). The response rates of angiofibromas at weeks 4, 8, and 12 of treatment were 0 each in the placebo group in contrast to 20% (95% CI, 8%-39%; P = .01), 43% (95% CI, 26%-63%; P < .001), and 60% (95% CI, 41%-77%; P < .001), respectively, in the sirolimus group. None of the 31 assessable patients in the placebo group were rated improved or better, and 26 of them (84%) were rated unchanged. In contrast, 5 (17%) and 13 (43%) patients in the sirolimus group were rated markedly improved and improved, respectively. Adverse events were mild to moderate and were observed in 27 (90%) and 22 (69%) patients in the sirolimus and placebo groups, respectively; however, none of the trial participants discontinued treatment. Acute pancreatitis developed as a serious adverse event in 1 patient in the sirolimus group, and the patient recovered soon after hospitalization without discontinuing treatment. Conclusions and Relevance: Sirolimus gel, 0.2%, demonstrated a significant clinical benefit for patients with TSC involving angiofibromas, thus providing a promising therapeutic modality. Trial Registration: ClinicalTrials.gov Identifier: NCT02635789.