Background: Abrocitinib, an oral Janus kinase 1 inhibitor, provided significant itch relief by week 2 in patients with moderate-to-severe atopic dermatitis (AD) in the phase III JADE COMPARE trial. Objectives: This post-hoc analysis of JADE COMPARE aimed to further characterize itch response and determined whether early itch relief could predict subsequent improvements in AD severity. Methods: JADE COMPARE was a randomized, double-blind, double-dummy, placebo-controlled trial. Adult patients (aged ≥ 18 years) with moderate-to-severe AD were randomly assigned to receive oral abrocitinib 200 mg or 100 mg once daily, subcutaneous dupilumab 300 mg every other week (after a 600-mg loading dose), or placebo, plus medicated topical therapy for 16 weeks. Assessments were ≥ 4-point improvement in Peak Pruritus Numerical Rating Scale (PP-NRS4) from days 2 to 15, Eczema Area and Severity Index (EASI), Investigator’s Global Assessment (IGA) response, and Dermatology Life Quality Index (DLQI) scores at week 12. Association between week 2 PP-NRS4 and efficacy at week 12 was evaluated by chi-squared tests. The predictive value of early response for later efficacy was assessed by area under the receiver operating characteristic curve. Results: As early as day 4 after treatment, a significantly greater proportion of patients achieved PP-NRS4 response with abrocitinib 200 mg (18.6%) versus dupilumab (5.6%; p < 0.001) and placebo (6.0%; p < 0.003). A similar trend was observed with abrocitinib at the 100-mg dose, with significantly greater PP-NRS4 response rates versus placebo as early as day 9. With both doses of abrocitinib, week 12 IGA 0/1, EASI-75, EASI-90, and DLQI 0/1 response rates were greater in week 2 PP-NRS4 responders than nonresponders; no differences were observed between week 2 PP-NRS4 responders and nonresponders in the dupilumab and placebo groups. Early improvement in PP-NRS at week 2 was associated with skin clearance at week 12 in abrocitinib-treated patients. Conclusions: Abrocitinib resulted in rapid relief from itch in patients with moderate-to-severe AD, with significant improvement in itch as early as day 4 after treatment with abrocitinib 200 mg compared with dupilumab and placebo. Abrocitinib-induced itch relief by week 2 was associated with subsequent improvements at week 12. [Video abstract available.] Trial registration: ClinicalTrials.gov identifier: NCT03720470. Video abstract: [MediaObject not available: see fulltext.].