Potentially inappropriate prescribing (PIP) is one of the major risk factors of adverse drug events in elderly patients. Pharmacotherapy assessment criteria may help reduce the instances of PIP among geriatric patients. This study aimed to verify the applicability of selected tools designed to assess prescribing appropriateness in elderly and to identify PIP in the study population. Based on pharmacist-led medication reviews that were performed among patients attending senior day-care centers based in Poland, aged 65 years and over, the following tools were applied for assessing the appropriateness of pharmacotherapy: PILA (patient-in-focus listing approach): STOPP/START v.2 and Amsterdam tool, DOLA (drug-oriented listing approach): PRISCUS list, and DOLA+: Beers criteria v.2019 and the EU(7)-PIM list–the criteria oriented on medications requiring indications. Fifty patients participated in the study. The prevalence of prescribing issues in the study population was very high and ranged from 28% to 100%, depending on the criteria applied. The highest number of PIP cases was identified based on the PILA criteria: STOPP/START v.2 (171, a mean of 3.4 PIP cases per patient), and the Amsterdam criteria (124, a mean of 2.5 PIP cases per patient). The lack of protective vaccinations against pneumococci identified using the START criterion was found to be the most common PIP (identified in 96% of the patients). Proton-pump inhibitors (PPIs) were identified as the most problematic group of medications. The STOPP, EU(7)-PIM and Beers criteria revealed cases of inappropriate prolonged PPI use, whereas the Amsterdam tool identified cases where PPIs should have been prescribed but were not. The highest number of PIP cases in the study population were identified with the PILA tools, and on this basis the most comprehensive assessment of pharmacotherapy appropriateness in geriatric patients was conducted. Further studies should be designed, covering a larger group of patients across different healthcare settings (inpatient and outpatient), with access to comprehensive patient data.