BACKGROUND/AIM: In a super-aging society, understanding frailty and potentially inappropriate medication (PIM) use is crucial for appropriate drug use in older persons. This study evaluated the association between frailty and PIMs in elderly hospitalized patients. PATIENTS AND METHODS: Patients ≥65 years who were admitted to Kameda Medical Center between October 2016 and 2017 were included. Frailty was defined as a Barthel Index <90 or Mini-Mental State Examination <18; patients not meeting these criteria were classified as non-frail. PIMs were defined according to the 2015 Beers Criteria. When PIMs were used at least once during hospitalization, patients were defined as PIM users; otherwise, they were defined as non-users. PIM users in both the frail and non-frail groups were compared through logistic regression analysis by adjusting for background factors and calculating adjusted odds ratios and 95% confidence intervals. As a sensitivity analysis, the frail group was subdivided into those with mild frailty and those with severe frailty, and the proportion of PIM users with mild frailty, severe frailty, and those without frailty were compared. RESULTS: The proportion of PIM users did not significantly differ between the groups with and without frailty (adjusted odds ratio=1.29, 95% confidence interval=0.84-1.98). As a result of sensitivity analysis, the proportion of PIM use was significantly higher in the group with severe frailty than in the non-frail group (adjusted odds ratio=12.0, 95% confidence interval=1.76-81.3). CONCLUSION: This study found no significant difference in PIM use between frail and non-frail elderly Japanese inpatients. However, sensitivity analysis revealed higher PIM use in those with severe frailty than in those who were non-frail. Therefore, this result implies that patients with severe frailty must be prescribed drugs appropriately, taking into account the background of each patient.