Introduction: Understanding functional hospital deterioration (HFD) as the loss of the capacity to perform at least one basic activity of daily life (BADL) at the time of hospital discharge respect to the baseline situation, understood as two weeks before the start of the acute disease. There are individual specific factors and others related to hospitalization that predispose the person to present functional hospital deterioration, which have an impact on the high rates of hospital readmissions, institutionalization and increased mortality. Objective: To estimate the factors that predict the development of hospital functional deterioration in adult patients older than 65 years hospitalized by the geriatric unit at the San Ignacio University Hospital in the period established between December 1, 2015 and December 31, 2017. Materials and Methods: Descriptive cross-sectional study of a hospital cohort from December 2015 to December 31, 2017. The univariate and multivariate analysis was carried out and the calculations were adjusted using the STATA program. Results: 1055 people were included. The prevalence of functional hospital deterioration was 41.14%, the average age was 85.58 years and the average Barthel prior to admission was 59. The three main factors associated with the development of functional hospital deterioration in the elderly population that consulted to San Ignacio University Hospital were: hospital stay [OR 1.88 IC95% (1.41-2.49) P <0.0001], malnutrition [OR 1.59 IC95% (1.16-2.19) P = 0.004] and delirium [OR 2.38 IC95% (1.83-3.10) P = <0.001]. Conclusion: The functional hospital deterioration is a highly prevalent condition in the geriatric population in our population, the factors associated with its development are the length of stay in hospital, malnutrition and delirium.