ImportanceMasculinizing gender-affirming hormonal therapy is associated with the development of acne. While isotretinoin is a highly effective acne treatment, little is known about its effectiveness and safety among transgender and gender-diverse individuals receiving gender-affirming hormonal therapy.ObjectiveTo evaluate clinical outcomes of isotretinoin among transgender and gender-diverse individuals receiving gender-affirming hormonal therapy.Design, Setting, and ParticipantsThis multicenter retrospective case series study was conducted at 4 medical centers: Mass General Brigham, University of Pennsylvania, Emory University, and Fenway Health. It included patients aged between 12 and 49 years who were receiving masculinizing gender-affirming hormonal therapy and prescribed isotretinoin for the management of acne between August 14, 2015, and September 20, 2023.ExposureIsotretinoin therapy for the management of acne.Main Outcomes and MeasuresThe percentage of patients experiencing improvement or clearance of acne, as well as rates of acne recurrence. Adverse effects and reasons for treatment discontinuation were also evaluated.ResultsAmong 55 included patients, the mean (SD) age was 25.4 years; 4 (7.3%) were Asian, 2 (3.6%) were Black, 4 (7.2%) were Hispanic, 1 was (1.8%) multiracial, and 36 (65.5%) were White. The median isotretinoin course duration was 6 months (IQR, 4.0-8.0), with a median cumulative dose of 132.7 mg/kg (IQR, 66.4-168.5); the cumulative dose was less than 90 mg/kg for 16 patients (29.1%) and less than 120 mg/kg for 22 patients (40.0%). Isotretinoin was associated with improvement in 48 patients (87.3%) and clearance in 26 patients (47.3%). For the 33 patients treated with a cumulative dose of 120 mg/kg or more, these rates increased to 32 patients (97.0%) and 21 patients (63.6%), respectively. Among the 20 patients who achieved acne clearance and had any subsequent health care encounters, the risk of recurrence was 20.0% (n = 4). The most frequently reported adverse effects were dryness (n = 44; 80.0%), joint pain (n = 8; 14.5%), and eczema (n = 5; 9.1%). Laboratory abnormalities were uncommon. Reasons for premature treatment discontinuation included cost, pharmacy issues, adverse effects, logistical reasons (scheduling), and wound healing concerns for gender-affirming surgery.Conclusion and RelevanceIn this case series study of individuals with acne who were receiving masculinizing gender-affirming hormonal therapy and underwent isotretinoin treatment, isotretinoin was often effective and well tolerated. However, premature treatment discontinuation was common and associated with poorer outcomes. Further efforts are needed to understand optimal dosing and treatment barriers to improve outcomes in transgender and gender-diverse individuals receiving masculinizing gender-affirming hormonal therapy.