Introduction/AimsTests for assessing upper extremity (UE) functional capacity in patients with Duchenne muscular dystrophy (DMD) are limited. This study aimed to evaluate the validity and reliability of the 6‐min pegboard and ring test (6PBRT) as a practical tool for this purpose.MethodsChildren with DMD (n = 22) were evaluated using the 6PBRT for UE functional capacity, the Quick Disabilities of the Arm, Shoulder, and Hand (Q‐DASH) for functionality, the Pediatric Quality of Life Inventory (PedsQL) for quality of life, and a dynamometer for handgrip strength and UE muscle strength.ResultsThe 6PBRT showed excellent test–retest reliability, with an intraclass correlation coefficient (ICC) of 0.978 (95% confidence interval, 0.946–0.984). A very strong positive correlation was observed between the test and retest 6PBRT mean scores (r = 0.981). The mean 6PBRT score exhibited moderate‐to‐strong correlations with handgrip strength (r = 0.653, r = 0.646, right/left, respectively), muscle strength (shoulder flexors [r = 0.793, r = 0.797, right/left, respectively], shoulder abductors (r = 0.763, r = 0.743, right/left, respectively), elbow flexors [r = 0.743, r = 0.755, right/left, respectively]), mean Q‐DASH score (r = −0.555), and mean PedsQL score (r = 0.611).DiscussionThe 6PBRT appears to be a valid and reliable measure for assessing upper extremity functional capacity in patients with DMD. This test is suitable for patients who are able to lift both hands above their heads.Trial Registration: NCT06174025