Although physical fitness is relevant for well-being and health, knowledge on the feasibility of instruments to measure physical fitness in older adults with intellectual disability (ID) is lacking. As part of the study Healthy Ageing with Intellectual Disabilities with 1,050 older clients with ID in three Dutch care services, the feasibility of 8 physical fitness tests was expressed in completion rates: box and block test, response time test, Berg balance scale, walking speed, grip strength, 30-s chair stand, 10-m incremental shuttle walking test, and the extended modified back saver sit and reach test. All tests had moderate to good feasibility in all subgroups, except for the participants with profound ID (all tests), severe ID (response time test and Berg balance scale), and wheelchair users (all tests that involve the legs). We conclude that the 8 tests are feasible to measure physical fitness in most older adults with ID.