Introduction: Overweight and obesity are recognized mortality risk factors in the general population. The aim of the study was to analyse the phenotypic distribution of body mass index (BMI), and to identify the prevalence of malnutrition and clinical and nutritional factors related to BMI in autonomous institutionalized elders. Material and Methods: Cross-sectional and descriptive study in 104 institutionalized aged people (73% female, mean of age 86.4 [±6.2] years and time on institutionalization 25.7 [±21.7] months). Mini-Nutritional Assessment (MNA), anthropometric measures and laboratory parameters were used for nutritional assessment. Bioimpedance analysis (BIA-101; RJL-System) was used for body composition analysis. The sample was classified into BMI tertiles (Tn): T1=<26.2kg/m2; T2=26.3-29.7kg/m2; and T3=≥29.8kg/m2. Results: The phenotypic distribution of BMI was: overweight 51% and, prevalence of obesity 29.8%. Mean of BMI: 28.3 (±4.6) kg/m2. Nutritional risk or malnutrition were 60.6% and 11.5%, respectively in the sample. The tertiles of BMI showed significant differences with: mid-arm muscle circumference, triceps-skinfold thickness, total body water (TBW) (all, p<0.001). Subjects into T1 had significantly higher nutritional risk or malnutrition compared with T2 and T3 counterparts (p=0.015). Waist-circumference, calf-circumference (at least, p<0.01), and TBW (p<0.001) were independent predictors of BMI in the linear regression analysis (R2=0.52). Conclusions: Overweight and obesity measured by BMI is not an exclusion criterion of malnutrition in the geriatric population. Nutritional screening by MNA and the conjoint use of clinical-nutritional parameters are useful for identifying at nutritional risk or malnutrition. Further studies are needed to define the potential nutritional risk factors associated with BMI in autonomous institutionalized aged.