Introduction: Low estimated Glomerular filtration rate (eGFR) is associated with functional decline. Little is known on that association in hospitalized elderly. Objective: Determine if low eGFR is associated with functional decline. Methods: Prospective cohort study that included 1826 patients 60 years and older hospitalized in a Geriatric Acute Unit, admitted between January 2012 and August 2015. The outcome was functional status assessed four times by the Barthel Index (BI). Kidney function was estimated by MDRD-4 IDMS and was grouped into four categories according to eGFR (normal ≥90, mild 60-89, moderate 59-30, severe <30). Multivariate logistic regression models and GLIMMIX procedure for longitudinal analyzes were used. Results: Mean age was 82.3±7.2 years, 51 % were women. In multivariate logistic regression, a BI≤60 at admission was associated with age ≥80, female gender, high comorbidity, social deterioration, hypoalbuminemia, anemia, MMSE<19, while the presence of mild or moderate renal failure reduced this risk. In the longitudinal analysis, lower total BI at follow-up was associated with age ≥80, female gender, social deterioration, hospital stay ≥15 days, high comorbidity, hypoalbuminemia, MMSE<19. The presence of mild, moderate or severe renal impairment was associated with higher BI over time. Conclusions: A low eGFR was associated with lower risk for functional decline at admission and overtime. These findings differ from previous reports in the literature.