Background <p>Cognitive behavioral therapy (CBT) is an effective treatment for childhood anxiety disorders, but few affected children receive CBT in routine care. To improve access, we previously developed a primary care-adapted stepped-care CBT protocol (Step-by-Step).</p> Objective <p>The primary aim of this study was to assess the feasibility of the trial design in preparation for a multi-site randomized non-inferiority trial. Secondary aims included assessing treatment acceptability and exploring preliminary clinical outcomes.</p> Methods <p>In a two-site randomized pilot trial in Swedish primary care, 32 children aged 7–12 years were allocated to stepped-care CBT (Step-by-Step, <i>n</i> = 16) or standard CBT (Cool Kids, <i>n</i> = 16). Feasibility outcomes included recruitment rate, waiting time, completion of sessions and assessments, protocol adherence, and therapist hours. Acceptability was assessed via treatment credibility and satisfaction. Clinical outcomes were clinician-rated anxiety severity and child- and parent-reported anxiety and depression.</p> Results <p>Recruitment rate, waiting time, therapist adherence, and completion rates were acceptable. Therapist hours per patient were 35% lower in Step-by-Step (3.9&#xa0;h) compared to Cool Kids (6&#xa0;h). Both treatments were rated as credible and satisfactory. Clinician-rated anxiety severity decreased significantly within both treatments (within-group pre–post effects: Step-by-Step, Cohen’s <i>d</i> = 1.63, 95% CI [1.10, 2.15] and Cool Kids, Cohen’s <i>d</i> = 0.99, 95% CI [0.59, 1.39]).</p> Conclusions <p>Trial feasibility data support progression to a non-inferiority trial. A stepped-care CBT protocol delivered in primary care was well accepted by participants and showed preliminary within-group improvements in anxiety outcomes, while requiring less therapist time than standard CBT.</p> Trial Registration Number <p>NCT05686512, 17 January 2023.</p>