Background: Knowledge of the extent of cognitive impairment among old age homeless people is very useful for policy-makers and mental health professionals. As there are few studies of this issue in Brazil, a cross-sectional study was carried among homeless people aged 65 years or over from Rio de Janeiro, Brazil. Methods: Data were collected on a random sample of 64 homeless people aged 65 years or over residents in a public hostel from Rio de Janeiro. Full data were collected by a trained researcher, using the Community Screening Instrument for Dementia (SCI-D) to appraise cognitive impairment, and The Mini Nutritional Assessment (MNA) to evaluate nutritional status. Results: The mean age was of 72.9 years (SD = 6,03 years). Most of the sample was male (71.9%), single (90.6%), from Rio de Janeiro (71.9%), illiterates (60.9%), unemployed (82.8%). The frequency of cognitive deficits was of 20.3%. 15.6% reported previous psychiatric admission, 12.5% presented malnutrition, 37.5% reported alcohol abuse/dependence. Conclusions: Specific measures should be implemented in the hostels. An example might be the creation of a multidisciplinary team to work specifically with old age homeless people in the hostels.