Background: Physical fitness is relevant for wellbeing and health, but knowledge on the feasibility and reliability of instruments to measure physical fitness for older adults with intellectual disability is lacking. Methods: Feasibility and test-retest reliability of a physical fitness test battery (Box and Block Test, Response Time Test, walking speed, grip strength, 30-s chair stand, 10-m Incremental Shuttle Walking Test and the Extended Modified Back-Saver Sit-and-Reach Test) were investigated in older adults with ID in a convenience sample of 36 older adults (mean 65.9, range 50-89 years), with differing levels of intellectual disability and mobility. Results and conclusion: All tests to measure physical fitness in older adults with ID had moderate to excellent feasibility and had sufficient test-retest reliability (ICCs 0.63-0.96). No statistically significant learning effects were found. (Contains 3 tables.)