Objective: Questions exist regarding the causal relationship between malnutrition and stroke outcomes. This study aimed to determine whether nutritional status changes or malnutrition during hospitalisation could predict 3-month outcomes in acute stroke patients. Methods: During a 10-month period, patients who suffered their first stroke within 7 days after stroke onset were included in this prospective multi-centre study. The demographic parameters, stroke risk and severity factors, malnutrition risk factors and dysphagia were recorded. Nutritional status was assessed by 3 anthropometric and 3 biochemical indices. Changes in nutritional status were defined by comparing the admission values with the 2-week values. A Modified Rankin Scale score of 3-6 was defined as a poor outcome at the 3-month follow-up. Univariate and multiple logistic regression analyses were used to investigate the power of nutritional status changes in predicting poor patient outcomes. Results: Data from 760 patients were analysed. Poor outcomes were observed in 264 (34.7%) patients. Malnutrition prevalence was 3.8% at admission and 7.5% after 2-weeks in hospital, which could not predict 3-month outcome. Emerging malnutrition was observed in 36 patients (4.7%) during the 2-week hospitalisation period and independently predicted poor 3- month outcomes after adjusting for confounding factors (odds ratio 1.37, 95% confidence interval, 1.03-1.83). Conclusions: Emerging malnutrition during hospitalisation independently predicted poor 3-month outcomes in acute stroke patients in this study.