Abstract Background Stapokibart is a novel anti-IL-4Rα monoclonal antibody approved for treating adults with moderate-to-severe AD. Objectives To assess the safety, efficacy, pharmacokinetics, pharmacodynamics, and immunogenicity of stapokibart in children with moderate-to-severe AD. Methods Multicenter, open-label, single-arm phase 1b/2a trial (NCT06162507) involving eight-week treatment and eight-week follow-up. Children aged 6–11 years received subcutaneous stapokibart based on a body weight-tiered regimen (30–60 kg: 300 mg Q3W for a total of three doses, including a 600 mg loading dose; 15–30 kg: 150 mg Q2W for a total of four doses, including a 300 mg loading dose). Results Twenty-five patients (30–60 kg: 13, 15–30 kg: 12) received stapokibart; 68.0% reported mild or moderate adverse events. At week 8, 53.8% of the 30–60 kg group and 75.0% of the 15–30 kg group achieved EASI-75. Stapokibart concentrations increased rapidly following the first dose, further climbed with repeated dosing, and gradually declined after treatment discontinuation. Stapokibart reduced inflammatory biomarkers in both groups. No treatment-related anti-drug antibodies were detected. No new safety signals emerged. Conclusions Stapokibart showed potential for improving disease outcomes and appeared to be well tolerated in children aged 6–11 years with moderate-to-severe AD. Larger controlled studies are needed to confirm long-term benefits.