BACKGROUND The economic benefit of the clinical pharmacist's role in ensuring the optimum use of medicines is potentially considerable, particularly when it comes to cancer management. We sought to evaluate the overall economic impact of clinical pharmacist interventions in the main cancer setting in Qatar. METHODS The total economic benefit of the clinical pharmacy interventions were analyzed from the public hospital perspective. Patient records in March 2018, July/August 2018, and January 2019 were retrospectively reviewed at the National Center for Cancer Care and Research, Qatar. The total benefit from interventions was the total cost avoidance due to preventable adverse drug events plus any cost savings associated with therapeutic-based resource use. Sensitivity analyses confirmed the results' robustness and increased generalizability. RESULTS A total of 1352 interventions based on 281 patients were analyzed. The majority of the drug-related problems were related to the appropriateness of therapy, followed by dosing and administration. The total population benefit over the 3-months study period was QAR 4,879,185 (USD 1,336,763), constituting cost avoidance of QAR 4,234,012 (USD 1,160,003) and negative resource-use cost savings of -QAR 645,174 (-USD 176,760). Projected annual overall benefit was QAR 14,355,354 (USD 3,932,974). The increase in resource use with therapies was mostly because of the addition of other medications. Cost avoidance was mostly driven by recommending additional medications and discontinuation of medications. The uncertainty analysis demonstrated the robustness of outcomes. CONCLUSIONS The clinical pharmacist intervention increased resource use and its cost. In overall, however, taking avoided cost of adverse drug events in consideration, it is an economically beneficial practice in the National Center for Cancer Care and Research setting, associated with adverse drug events prevention and substantial economic benefits.