Abstract Background The 5-repetition chair stand test (CST) is increasingly being used to assess locomotion capacity in older adults. However, there is a lack of age-stratified cutoffs for adults aged ≥70 validated against a higher risk of functional loss. Methods We used 2 population-based studies (Study on global AGEing and adult health in Mexico [SAGE Mexico] and Toledo Study for Healthy Aging [TSHA]) and receiver operating characteristic (ROC) analyses to develop and cross-validate age-stratified chair stand cutoffs with activities of daily living (ADL) disability as the outcome. Then, we used data from an randomized controlled trial (RCT) (Multidomain Alzheimer Preventive Trial [MAPT]) and a frailty day-hospital for external validation with cross-sectional and longitudinal measures of ADL disability. The merged sample of SAGE Mexico and TSHA was n = 1 595; sample sizes for external validation were: MAPT n = 1 573 and Frailty day-hospital n = 2 434. The Cox models for incident disability in MAPT had a mean follow-up of 58.6 months. Results Cutoffs obtained were 14 second (ages 70–79) and 16 second (ages 80+). Those cutoffs identified older adults at higher odds of incident ADL disability odds ratio (OR) = 1.72 (95% confidence interval [CI] 1.06; 2.78) for ages 70–79 and odds ratio (OR) = 2.27 (95% CI 1.07; 4.80) in those aged 80+. Being a slow chair stander according to the cut points was associated with ADL disability in cross-sectional and longitudinal measures. Conclusions Fourteen- and 16-second cut points for the CST are suitable to identify people at higher risk of functional decline among older adults in Mexico and Toledo, Spain. Adjusting the cut point from 14 to 16 second generally improved the psychometric properties of the test. The validation of these cutoffs can facilitate the screening for limited mobility and the implementation of the Integrated Care for Older People program.