The elderly population and the incidence of chronic diseases are growing rapidly in Brazil. This raises the demand for health services (like Nursing Homes - NH) and drugs, exposing this population to Potential Drug Therapy Problems (PDTP). A cross-sectional study in a Brazilian NH was developed through prescription analyses. PDTP were accounted when one of the following were detected: double therapy (DT); sub-dose; overdose; drug-drug interaction (DDI); food-drug interaction (FDI); Potentially Inappropriate Medication (PIM) according to the Beers Criteria; PIM according to the STOPP (Screening Tool for Older Persons’ prescriptions). 116 PDTP were identified (17 DT, 16 sub-doses, an overdose, 52 DDI, 10 FDI, and 20 PIM according to Beers). With the STOPP, 143 PDTP were detected. Safety PDTP were the most frequent. The high number of PDTP detected indicates a low level of quality of the prescriptions, showing the need for the pharmacist work towards elderly drug therapy upgrade.