Background: Two identical phase 3 randomized, double-blind, vehicle-controlled, 12-week studies (NCT03168321 and NCT03168334) demonstrated the efficacy and safety of tazarotene 0.045% lotion in participants with moderate-to-severe acne. Data from these studies were pooled and analyzed post hoc to evaluate outcomes by sex. Methods: Patients aged ≥9 years with moderate-to-severe acne (score 3 or 4 on the Evaluator's Global Severity Score [EGSS]) were randomized (1:1) to once-daily tazarotene 0.045% lotion or vehicle lotion for 12 weeks. Outcomes comprised inflammatory/noninflammatory lesion counts, treatment success (proportion of participants achieving ≥2-grade reduction from baseline in EGSS and score of 0 [“clear”] or 1 [“almost clear”]), and treatment-emergent adverse events (TEAEs). Results: A total of 1,064 females and 550 males were included in this analysis. For both sexes, least-squares mean percent changes from baseline to week 12 in lesion counts were significantly greater with tazarotene 0.045% lotion versus vehicle (inflammatory: females, -60.1% vs -52.1%; males, -53.6% vs -39.8%; noninflammatory: females, -57.6% vs -44.9%; males, -52.9% vs -36.5%; P<0.001, all). The percentage of participants achieving treatment success at week 12 was also significantly higher with tazarotene 0.045% lotion versus vehicle in females and males (P<0.001, both). Compared with tazarotene-treated males, tazarotene-treated females had significantly greater changes from baseline in inflammatory and noninflammatory lesions and a greater proportion achieved treatment success at week 12 (P<0.05, all). TEAE rates were similar between tazarotene- and vehicle-treated males; rates were higher for tazarotene-treated females than vehicle-treated females. Conclusions: Tazarotene 0.045% lotion was efficacious and well tolerated in the treatment of moderate-to-severe acne in female and male participants. J Drugs Dermatol. 2020;19(8): doi:10.36849/JDD.2020.5249