- Purpose To evaluate the influence of patient’s weight on rehabilitation outcomes in first-event stroke patients. Design Retrospective, observational comparative study. 102 first-time stroke male and female patients admitted to the 52-bed neurology rehabilitation department in a rehabilitation hospital were included in the study. Body mass index (BMI), Functional Independence Measure (FIM) on admission and at discharge, as well as the delta-FIM (FIM on admission – FIM at discharge) were evaluated. The Kruskal–Wallis test was used to compare the FIM and the NIHSS scores between BMI groups (normal, overweight, moderate and severe obesity). Results A statistically significant negative correlation (rho = −0.20, p = 0.049) was found between FIM change and BMI, that remained significant after adjustments for age, sex and hospitalisation days. No difference was found between groups in FIM or NIHSS change between BMI groups. Conclusions In sub-acute post-stroke patients undergoing rehabilitation in rehabilitation hospital, BMI was negatively associated with the improvement of functional parameters. Patients’ BMI should be taken into consideration when predicting rehabilitation outcome for stroke patients. Further investigations are needed to identify the functional parameters affected by the patients’ BMI.Implications for RehabilitationIn sub-acute post-stroke patients undergoing rehabilitation in rehabilitation hospital, BMI was negatively associated with the improvement of functional parameters.Patients’ BMI should be taken into consideration when predicting rehabilitation outcome for stroke patients.New rehabilitation strategies should be designed to improve the functional outcomes of rehabilitation of obese patients.