Objective To validate the “International Fitness Scale” (IFIS) in older adults. Methods Firstly, cognitive interviews were performed to ensure that the questionnaire was comprehensive for older Chilean adults. After that, a transversal study of 401 institutionalized and non-institutionalized older adults from Maule region in Chile was conducted. A battery of validated fitness tests for this population was used in order to compare the responses obtained in the IFIS with the objectively measured fitness performance (back scratch, chair sit-and-reach, handgrip, 30-s chair stand, timed up-and-go and 6-min walking). Results Indicated that IFIS presented a high compliance in the comprehension of the items which defined it, and it was able of categorizing older adults according to their measured physical fitness levels. The analysis of covariance ANCOVA adjusted by sex and age showed a concordance between IFIS and the score in physical fitness tests. Conclusion Based on the results of this study, IFIS questionnaire is a good alternative to assess physical fitness in older adults.