OBJECTIVES: To investigate the effect of motivation on improvements in the Functional Independence Measure (FIM) scores in subacute stroke patients with cognitive impairment. METHODS: This retrospective cohort study included 358 consecutive subacute stroke patients with first-ever stroke and Mini-Mental State Examination score ≤23 at admission. We determined motivation and rehabilitation outcome using the vitality index and FIM-motor gain, respectively. Stepwise multiple regression analysis was performed to identify the factors at admission related to FIM-motor gain. RESULTS: Of 80 participants enrolled in this study (mean age: 74.2 ± 11.3 years). The median (interquartile range) vitality index at admission and FIM-motor gain were 7 (4) and 23 (22) points, respectively. Stepwise multiple regression analysis revealed that age (B, -0.43; 95% confidence interval [CI], -0.65-(-0.21); β, -0.31; P <.001), duration from stroke onset to admission (B, -0.18; 95% CI, -0.33-(-0.04); β, -0.20; P =.014) and Stroke Impairment Assessment Set-motor function (B, 1.27; 95% CI, 0.92-1.61; β, 0.78; P <.001), FIM-motor (B, -0.80; 95% CI, -1.01-(-0.60); β, -0.95; P <.001), and vitality index (B, 3.79; 95% CI, 2.37-5.21; β, 0.50; P <.001) scores at admission were significantly associated with the FIM-motor gain. DISCUSSION: The vitality index was significantly associated with FIM improvement in subacute stroke patients with cognitive impairment.