Background: Timed up and go (TUG) and sit to stand (STS) tests that required less space and easier to be performed in respiratory and cardiac diseases for assessing functionality. Aim was to test the reliability of TUG and 30-second STS (30STS) tests and determine the validity of TUG and 30STS tests in patients with Pulmonary Hypertension (PH). Methods: Thirty-eight patients with diagnosed PH were included. We collected TUG, 30STS, quadriceps muscle strength, physical activity level, and 6MWT. Intra-class correlation coefficient (ICC) was used to determine test-retest reliability and correlations with quadriceps muscle strength, physical activity level and 6MWT for validity of the TUG and 30STS tests. Results: The TUG and 30STS tests were associated with age, functional class, muscle strength, physical activity and functional exercise capacity in patients with PAH (p < 0.05). 6MWT was associated with age, functional class, muscle strength, physical activity and functional exercise capacity (p < 0.05). ICC (95%) for TUG test and 30STS were 0.96 (0.93–0.98) and 0.95 (0.90–0.97), respectively. Conclusions: The TUG and 30STS tests were reliable and valid tests for measuring physical performance in PH. This study supports using the TUG and 30STS tests as practical assessment tools in patients with PH.