UNLABELLED: To characterize and compare the post-marketing safety profiles of Janus kinase (JAK) inhibitors used in alopecia areata (AA), including tofacitinib, baricitinib, ruxolitinib, and ritlecitinib. METHODS: Reports associated with JAK inhibitors in AA (2015-2025) were retrieved from the FDA Adverse Event Reporting System (FAERS). Disproportionality analyses utilized within-class and external non-JAK comparisons. Additionally, time-to-onset (TTO), serious adverse event (SAE) profiles, and sensitivity analyses were assessed. RESULTS: Among 1,905 identified reports (baricitinib [n = 881], ritlecitinib [n = 515], tofacitinib [n = 489], ruxolitinib [n = 20]), safety signals varied across agents. Tofacitinib showed signals involving neuropsychiatric and autoimmune events; baricitinib was associated with thrombocytosis, deep vein thrombosis, and breast cancer; ruxolitinib with pyrexia and elevated blood cholesterol; and ritlecitinib with gastrointestinal events and creatine phosphokinase elevation. TTO patterns were also heterogeneous, with earlier onset for tofacitinib and ruxolitinib, clustering within the first month for ritlecitinib, and a relatively delayed onset for baricitinib. Across the class, serious outcomes were most commonly related to infections, although the distribution of clinical outcomes differed by agent. CONCLUSIONS: JAK inhibitors used in AA demonstrated heterogeneous post-marketing safety patterns not fully captured by class-level warnings. These findings support agent-specific surveillance and individualized risk assessment in clinical practice.