Background Geriatric outpatients with polypharmacy have a high risk of potentially inappropriate medication (PIM) use. Aim To identify differences in both prevalence and patterns of PIMs and drug-related problems (DRPs) in older outpatients who visited the tertiary hospitals (THs) and community health centers (CHCs) and analyze associated factors. Method A prospective cross-sectional study was conducted in five THs and five CHCs from September 2018 to November 2019 in Beijing, China. Data were collected from outpatients aged ≥ 65 years with chronic diseases and polypharmacy. PIMs were evaluated using the 2015 and 2019 Beers Criteria and the Screening Tool of Older Persons' Prescriptions (STOPP) criteria. DRPs were classified using the Helper-Strand DRP Classification. The prevalence and types of PIMs and DRPs were compared, and relevant factors were analyzed. Results The prevalence of PIMs based on the 2015 Beers Criteria was higher in patients from the THs, while PIMs based on the 2019 Beers Criteria did not show a significant difference. PIM prevalence based on STOPP Criteria and DRPs was higher in patients from CHCs. Visiting CHCs was an independent factor of PIMs based on the 2015 Beers Criteria (OR 0.774, 95% CI 0.604-0.992) and the STOPP Criteria (OR 2.427, 95% CI 1.883-3.128), and DRPs (OR 3.612, 95% CI 2.682-4.865). Conclusion Differences in PIM and DRP might be due to the patients and settings. Specific measures to improve the appropriateness of medications in both settings should be used.© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.