<b><i>Introduction:</i></b> Clinical pharmacist (CP) intervention improves drug prescription by identifying potentially inappropriate prescriptions (PIPs). Geriatric perioperative care units (UPOGs) provide enhanced care for patients with hip fracture, including drug prescription. However, it is not known whether adding a CP intervention in a UPOG decreases the number of PIPs. This study aimed to evaluate the effect of a CP intervention, combining an implicit and an explicit method, on the number of PIPs in a UPOG. <b><i>Methods:</i></b> This single centre before-after-control-impact study recruited patients aged over 75 years admitted to a UPOG for a hip fracture. The “control group” (“before period”) received usual care including two medication reconciliations, one at admission and one at discharge. The “intervention group” (“after period”) received usual care and a CP intervention including two medication reconciliations, a medication review with two tools, STOPP/START and Medication Appropriateness Index, and a meeting between a CP and geriatricians. PIPs were assessed in both groups by STOPP/START and Medication Appropriateness Index and compared from hospital admission to discharge. <b><i>Results:</i></b> A total of 209 patients were included, 150 in the control group and 59 in the intervention group (mean age: 87.2 ± 5.9 years). The number of PIPs decreased in both groups from hospital admission to discharge (<i>p</i> < 0.001). The number of PIPs, potentially inappropriate medications, and potential prescribing omissions decreased more in the intervention group than in the control group (adjusted intervention effect: −2.46 (95% CI: −2.63; −2.24); −1.13 (95% CI: −1.27; −0.98); and −1.35 (95% CI: −1.52; −1.18), respectively, <i>p</i> < 0.001 for all). <b><i>Discussion/Conclusion:</i></b> A CP intervention with an explicit and implicit method improved prescriptions in a UPOG. Further randomized studies are necessary to evaluate the effect of a CP intervention on adverse drug events, health costs, and mortality.