Aim This study aimed to evaluate the efficacy of pharmacists' assessment and intervention using the Screening Tool for Older Persons' Appropriate Prescriptions for Japanese (STOPP‐J) to detect and correct potentially inappropriate medications (PIM) compared with the Screening Tool of Older Persons' Potentially Inappropriate Prescriptions (STOPP) criteria version 2. Methods A prospective observational study was carried out at a medical unit of Cardiovascular Surgery and Cardiovascular Internal Medicine in a Japanese university hospital involving new inpatients aged ≥65 years prescribed one or more daily medication. Pharmacists detected PIM based on STOPP‐J and STOPP criteria version 2, and corrected them with physicians. The number of patients with PIM, the content and changes in PIM were compared between both criteria. Results Overall, 230 patients were included (mean age 75.4 years, 162 men, mean number of medications 8.3). STOPP‐J detected significantly more patients with PIM than STOPP criteria version 2 (122 [53%] vs 75 [33%], P < 0.001). The number of PIM based on STOPP‐J was 232, the physicians were recommended to change 61 (26%) and 50 (22%) were changed. Meanwhile, the number of PIM based on STOPP criteria version 2 was 133, the physicians were recommended to change 61 (46%) and 54 (41%) were changed. Several medications detected as PIM using STOPP‐J were not detected using STOPP criteria version 2. Conclusions STOPP‐J detected significantly more patients with PIM than STOPP criteria version 2, and pharmacists' assessment and intervention based on STOPP‐J were suggested to be effective for detecting and correcting PIM. Geriatr Gerontol Int 2019; 19: 1101–1107.