Abstract Introduction & Objectives Janus kinase (JAK) inhibition is a promising approach for the treatment of vitiligo. Here, we report the clinical efficacy and safety of upadacitinib (UPA), an oral JAK inhibitor, in a phase 2b multicenter, randomized, double-blind, placebo-controlled study of adults with extensive non-segmental vitiligo (NSV). Materials & Methods Eligible patients were aged 18–65 years with NSV, a Facial Vitiligo Area Scoring Index (F-VASI) of ≥0.5, and a Total Vitiligo Area Scoring Index (T-VASI) of ≥5 at baseline. This 52-week study (NCT04927975) comprised 2 periods. In period 1, patients were randomly assigned to once daily UPA 22 mg (UPA22), UPA 11 mg (UPA11), UPA 6 mg (UPA6), or placebo (PBO) for 24 weeks of treatment. In a 28-week blinded extension (period 2), patients receiving UPA during period 1 continued their respective regimens; patients who received PBO in period 1 were pre-assigned to either UPA11 or UPA22. Clinical efficacy endpoints evaluated through week 36 included percent change from baseline (%CFB) in F-VASI (week 24, primary endpoint), reductions from baseline in F-VASI of ≥50% (F-VASI 50) and ≥75% (F-VASI 75), %CFB in T-VASI, and reduction from baseline in T-VASI of ≥50% (T-VASI 50). Safety data as of January 13, 2023 (data cutoff date) are presented. Results Of the 185 patients enrolled in period 1, 165 (89.2%) continued to period 2. At baseline, 68% of patients had extensive vitiligo (T-VASI > 10), and 71% had active vitiligo. At week 24, the %CFB in F-VASI was greater with UPA11 (−35.6%) and UPA22 (−34.0%) vs PBO (−14.4%; nominal P = .005 and P = .013, respectively). A greater proportion of patients achieved F-VASI 50 and F-VASI 75 with UPA11 (38.3%, 19.1%) and UPA22 (39.5%, 14.0%) vs PBO (10.9%, 2.2%; nominal P < .05 for both doses and for both endpoints). Likewise, the %CFB in T-VASI was greater with UPA11 (−17.3%) and UPA22 (−20.7%) vs PBO (−6.4%; nominal P = .026 and P = .005, respectively). A higher percentage of patients achieved T-VASI 50 with UPA22 (11.6%) than with PBO (2.2%; nominal P = .027). UPA efficacy continued to improve through week 36, with %CFB in F-VASI for UPA6, UPA11, and UPA22 of −20.8%, −44.9% and −47.7%, respectively. At week 36, F-VASI 50 was achieved with UPA6, UPA11, and UPA22 by 34.2%, 54.3% and 61.5% of patients and F-VASI 75 by 15.8%, 40.0%, and 30.8%, respectively. At week 36, %CFB in T-VASI for UPA6, UPA11 and UPA22 were −24.3%, −32.0% and −37.6%, with 10.5%, 20.0% and 19.2% of patients, respectively, achieving T-VASI 50. Treatment-emergent adverse event (TEAE) rates were generally similar with UPA and PBO in period 1 (most common TEAEs: COVID-19, acne, fatigue, and headache) and were similar across treatment arms in period 2. One death adjudicated as undetermined/unknown cause and deemed by the investigator to have no reasonable possibility of being related to study drug occurred in the UPA22 group (period 1). One adjudicated event of nonfatal ischemic stroke occurred with UPA11 (period 2). There were no adjudicated events of venous thromboembolism, gastrointestinal perforation, or events of opportunistic infection, active tuberculosis, or malignancy. Conclusion Treatment with UPA for 24 weeks resulted in greater improvements vs PBO in the clinical outcomes of adults with extensive NSV. Observed clinical efficacy continued to improve through week 36 with UPA treatment. UPA was generally well tolerated, with no new safety signals identified.