To study the responsiveness of the International Classification of Functioning, Disability, and Health (ICF) core set with respect to human functioning and disability in stroke patients. Postacute stroke patients who were admitted to the convalescent rehabilitation wards were included in this observational cohort study. The comprehensive ICF core set for neurological conditions for postacute care and the ICF rehabilitation set were evaluated at admission and discharge using five-grade qualifiers. Extension indexes were calculated for entire two ICF core sets. Responsiveness was measured as change in the extension indexes in the ICF core sets. The correlation between changes in ICF core sets and improvement in the Functional Independence Measure (FIM) was analyzed using Spearman’s correlation coefficient. The study included 108 poststroke patients (49 women, mean age 70.8 years, mean FIM score improvement: 23.0). The mean percentage of categories that showed changes with at least one qualifier level was 19.5% in the comprehensive ICF core set for neurological conditions for postacute care and 35.9% in the ICF rehabilitation set. Effect sizes in each ICF core set were moderate to large (0.79–0.80). Improvement in the two ICF core sets correlated significantly with changes in the FIM score. Our results indicate that functioning and disability parts of these two ICF core sets can detect changes in functioning and disability in patients who receive an inpatient rehabilitation program for postacute stroke.