Proton pump inhibitors are considered potentially inappropriate medications in the geriatric population. The use of proton pump inhibitors by older adults has increased over the past several decades; however, existing literature suggests that only one-third of patients prescribed these medications have a valid indication for use. The aim of this study was to assess the appropriateness of proton pump inhibitor therapy in a population of ambulatory geriatric patients and to determine the impact of an interdisciplinary clinic on their use. This was a retrospective, cross-sectional study of patients referred to an ambulatory geriatrics clinic between October 2017 and March 2021. Participants were eligible for inclusion if they were taking a proton pump inhibitor at the time of clinic admission. Appropriateness of proton pump inhibitor therapy was assessed based on indication and dosing regimen. In total, 280 participants were included. The mean age was 79.6 years (SD 7.7) and 60% were female. Overall, 94 of 280 (33.6%) participants had a documented valid indication for their proton pump inhibitor. The clinic team intervened to reduce the dose or discontinue 76 of 186 (40.8%) inappropriate proton pump inhibitors. Only one-third of proton pump inhibitors used by ambulatory geriatric patients have a documented appropriate indication for use. Given the medical complexity of this population and their vulnerability to adverse effects, the ambulatory geriatric population should be a priority target for proton pump inhibitor deprescribing initiatives.