Abstract Background Adequate and user-friendly instruments for assessing physical function and disability in older adults are vital for estimating and predicting health care needs in clinical practice. The Late-Life Function and Disability Instrument Computer Adaptive Test (LLFDI-CAT) is a promising instrument for assessing physical function and disability in gerontology research and clinical practice. Objective The aims of this study were: (1) to translate the LLFDI-CAT to the Dutch language and (2) to investigate its validity and reliability in a sample of older adults who spoke Dutch and dwelled in the community. Design For the assessment of validity of the LLFDI-CAT, a cross-sectional design was used. To assess reliability, measurement of the LLFDI-CAT was repeated in the same sample. Methods The item bank of the LLFDI-CAT was translated with a forward-backward procedure. A sample of 54 older adults completed the LLFDI-CAT, World Health Organization Disability Assessment Schedule 2.0, RAND 36-Item Short-Form Health Survey physical functioning scale (10 items), and 10-Meter Walk Test. The LLFDI-CAT was repeated in 2 to 8 days (mean=4.5 days). Pearson's r and the intraclass correlation coefficient (ICC) (2,1) were calculated to assess validity, group-level reliability, and participant-level reliability. Results A correlation of .74 for the LLFDI-CAT function scale and the RAND 36-Item Short-Form Health Survey physical functioning scale (10 items) was found. The correlations of the LLFDI-CAT disability scale with the World Health Organization Disability Assessment Schedule 2.0 and the 10-Meter Walk Test were −.57 and −.53, respectively. The ICC (2,1) of the LLFDI-CAT function scale was .84, with a group-level reliability score of .85. The ICC (2,1) of the LLFDI-CAT disability scale was .76, with a group-level reliability score of .81. Limitations The high percentage of women in the study and the exclusion of older adults with recent joint replacement or hospitalization limit the generalizability of the results. ...