Introduction: Attention-deficit/hyperactivity disorder (ADHD) affects 5–7% of children globally . Pharmacological treatments are limited by adverse effects and poor long-term adherence. Game-based digital therapeutics (DTx) offer a promising adjunctive approach. Objectives: This study aimed to evaluate the preliminary efficacy and safety of Focus Run, a novel DTx designed to improve core symptoms and executive function in children with ADHD. Methods: This prospective single-arm pilot study enrolled 25 children aged 4–14 years. Participants completed a 4-week homebased intervention (25 min/day , 5 days/week). Outcomes were assessed at baseline and week 4, including the Swanson, Nolan, and Pelham Rating Scale(SNAP-IV), Weiss Functional Impairment Rating Scale(WFIRS), Behavior Rating Inventory of Executive Function(BRIEF), cognitive tests (DCT, BOKE STARS), and prefrontal hemodynamics via fNIRS during a Go/ No-Go task. Results: After the 4-week intervention, the SNAP-IV total score decreased significantly (mean reduction 7 .96 points, P < 0.001, Cohen's d = 1.17), with the largest effect on inattention (d = 1.30). WFIRS and BRIEF domains improved (P < 0.05). DCT accuracy increased (P < 0.001). fNIRS showed enhanced Go trial accuracy (P < 0.001) without significant hemodynamic changes. Completion rate was 100%, mean adherence 110.6%, and parent satisfaction 72%. Three participants (12%) reported mild transient visual fatigue; no serious adverse events occurred. Conclusions: This study demonstrated that Focus Run was safe and highly adherent in children with ADHD. Significant reductions in core symptoms and improvements in executive function were observed. These preliminary findings support further investigation of Focus Run as an adjunctive intervention in randomized controlled trials.