Background: Upadacitinib is a selective reversible Janus kinase (JAK) inhibitor with established efficacy in moderate-to-severe atopic dermatitis (AD). Objective: We evaluated the safety of upadacitinib in patients with moderate-to-severe AD. Methods: Integrated safety data from the 16-week placebo-controlled periods of 1 phase 2b and 3 ongoing phase 3 studies (16 weeks) and longer-term safety data from patients receiving upadacitinib during the blinded extension periods of the three phase 3 studies were analyzed (all upadacitinib exposure). Treatment-emergent adverse events (TEAEs) were presented as exposure-adjusted rates per 100 patient-years (PY). Results: Safety results were similar between the 16-week and all upadacitinib exposure groups. The latter group included 2485 patients (333 adolescents), receiving upadacitinib 15 mg (n = 1239) or 30 mg (n = 1246) for a mean duration of approximately 1 year. Upadacitinib was well tolerated by both adults and adolescents. TEAEs and discontinuation due to AEs were reported more frequently in patients receiving 30 mg upadacitinib (respectively, 311.9 and 5.7 events per 100 PY) versus 15 mg (respectively, 274.6 and 4.4 events per 100 PY). Serious adverse event rates (15/30 mg, 7.1/7.7 events per 100 PY) were similar in both groups. Acne was the most frequently reported adverse event (15/30 mg, 13.3/20.2 events per 100 PY). Serious infection rates were similar across treatment groups. Adjudicated major adverse cardiovascular event and venous thromboembolic event rates were ≤0.1 events per 100 PY. Rates of malignant neoplasms were within the expected range for the general population. Conclusions: Upadacitinib was well tolerated, and no new important safety risks were observed among adults and adolescents with moderate-to-severe AD treated for approximately 1 year compared to the known safety profile of upadacitinib.