Background: Obesity paradox has been reported because of the inverse relationship between the body mass index (BMI) and mortality in stroke patients. The relationship between BMI and functional recovery in stroke survivors is less well established. We explored the impact of BMI on functional recovery and mortality in stroke patients in the China National Stroke Registry (CNSR). Methods: Patients were consecutively recruited based on a standard protocol and prospectively followed up for outcomes at 3 months after disease onset. Patients were divided into 5 groups according to their BMI: underweight (<18.5 kg/m(2)), normal weight (18.5-22.9 kg/m(2)), overweight (23-27.4 kg/m(2)), obese (27.5-32.4 kg/m(2)), or severely obese (>= 32.5 kg/m(2)). Multivariate logistic regression was performed to analyze the association between BMI and functional recovery or mortality. Results: CNSR enrolled 22,216 patients hospitalized for acute cerebrovascular events, and 10,905 eligible acute ischemic stroke patients were analyzed in our study. Favorable functional recovery (modified Rankin Scale score 0-1) was seen in 52.4% of underweight, 55.0% of normal weight, 61.0% of overweight, 59.2% of obese, and 60.3% of severely obese stroke survivors (P < .001). Overweight was independently associated with favorable 3-month functional recovery (odds ratio [OR] 1.24; 95% confidence interval [CI] 1.12-1.38). Mortality rate was 14.9% in underweight, 7.8% in normal weight, 7.1% in overweight, 7.2% in obese, and 11.5% in severely obese patients (P < .001). Severe obesity was independently associated with higher 3-month mortality (OR 2.01; 95% CI 1.10-3.69). Conclusions: The stroke obesity paradox can be extended to include functional recovery but should not be interpreted as the fatter the better.