Background: This study investigated the completion rates, scores and factors associated with non-completion and low scores on physical capability tests in a health survey administered to adults with intellectual disabilities. Method: Assessment comprised body mass index (BMI), the Short Physical Performance Battery (SPPB), the timed up-and-go (TUG) test, the one-legged stance (OLS) test; and gross motor, communication and behavioural functioning tests. Results: The completion rates among 93 participants (aged 17-78) were 46% for the SPPB, 42% for the TUG, and 31% for the OLS. More severe intellectual disability (OR = 3.12, p < 0.001) and lower BMI (OR = 0.859, p = 0.001) were related to test non-completion. The SPPB scores were below the reference values from the general population. Lower scores were associated with older age, motor disabilities and intellectual disability severity. Conclusions: Including physical capability tests in health surveys among adults with intellectual disabilities is important to monitor functional status and guide prevention strategies.