Purpose: Patients with pulmonary hypertension (PH) may have limitations in the upper extremity function. This study aimed to investigate the validity and reliability of the 6-minute pegboard ring test (6PBRT) in patients with pulmonary hypertension PH. Methods: This study included 31 patients with PH. The upper extremity function was measured using the 6PBRT. Muscle strength was assessed for shoulder flexor, shoulder abductor, elbow extensor, and elbow flexors muscles using with a digital dynamometer, and handgrip strength using the hand dynamometer. Limitation of the activities of daily living was evaluated using the Milliken Activities of Daily Living Scale. The intra-class correlation coefficient (ICC) was used to determine test-retest reliability. Results: The 6PBRT showed excellent test-retest reliability with the ICC=0.98 (95% CI 0.82–0.99). The standard error of measurement (SEM) and minimal detectable change (MDC) was calculated as 5.9 and 16.4, respectively. The patients with New York Heart Association (NYHA) Class III had significantly lower scores in the 6PBRT compared to the patients with Class II showing the known-groups validity of the 6PBRT (p=0.005). The 6PBRT was significantly and strongly correlated with age (r=-0.628, p<0.001), functional class (r=-0.502, p=0.004), activities of daily living (r=0.522, p=0.003), moderately correlated with dominant side shoulder flexor (r=0.360, p=0.047), shoulder abductor (r=0.388, p=0.031), elbow flexor (r=0.406, p=0.036) and handgrip muscles strength (r=0.375, p=0.041). Conclusion: This study showed that 6PBRT has excellent test-retest reliability and good validity, including known-groups and convergent in PH. These results support the use of 6PBRT as a practical upper extremity performance assessment tool in patients with PH.