Clinical trials showed that upadacitinib, a selective Janus kinase-1 inhibitor, is effective for treatment of moderate-to-severe atopic dermatitis. However, daily practice studies are limited. This multicentre prospective study evaluated the effectiveness of 16 weeks of upadacitinib treatment for moderate-to-severe atopic dermatitis in adult patients, including those with previous inadequate response to dupilumab and/or baricitinib, in daily practice. A total of 47 patients from the Dutch BioDay registry treated with upadacitinib were included. Patients were evaluated at baseline, and after 4, 8 and 16 weeks of treatment. Effectiveness was assessed by clinician- and patient-reported outcome measurements. Safety was assessed by adverse events and laboratory assessments. Overall, the probabilities (95% confidence intervals) of achieving Eczema Area and Severity Index ≤ 7 and Numerical Rating Scale - pruritus ≤ 4 were 73.0% (53.7-86.3) and 69.4% (48.7-84.4), respectively. The effectiveness of upadacitinib was comparable in patients with inadequate response to dupilumab and/or baricitinib and in patients who were naïve for these treatments or who had stopped such treatments due to adverse events. Fourteen (29.8%) patients discontinued upadacitinib due to ineffectiveness, adverse events or both (8.5%, 14.9% and 6.4%, respectively). Most frequently reported adverse events were acneiform eruptions (n = 10, 21.3%), herpes simplex (n = 6, 12.8%), nausea and airway infections (both n = 4, 8.5%). In conclusion, upadacitinib is an effective treatment for patients with moderate-to-severe atopic dermatitis, including those with previous inadequate response to dupilumab and/or baricitinib treatment.