<b><i>Introduction:</i></b> A Choosing Wisely campaign (CWC) was implemented at King Khalid General Hospital in the Hafr Albatin region of Saudi Arabia to reduce unnecessary overuse of medical services. The aim of this study was to assess the effect of the campaign on reducing three specifically targeted services. <b><i>Methods:</i></b> The study followed a quasi-experimental pre-post design at the King Khalid General Hospital. The population included all hospital encounters with patients visiting the hospital from October 2019 to January 2020 (preintervention phase) and those visiting during February 2020 (postintervention phase). The collected variables included: the number of patient encounters where creatine kinase-myocardial band analyses was performed, the results of creatine kinase-myocardial band analyses performed, the number of patient encounters where brain computed tomography scans was performed, results of the performed brain computed tomography scans, and the number of patient encounters where amoxicillin clavulanic acid was prescribed. Relative risks were calculated to compare the proportions of the pre- and postintervention periods. <b><i>Results:</i></b> Our results showed a reduction in the use of three unnecessary services following the implementation of the CWC coupled with improved diagnostic yield. Postintervention, the proportion of patient encounters where creatine kinase-myocardial band analyses were performed declined from 7.1% to 6% (relative risk: 0.84, 95% CI: 0.78–0.91), and the proportion of creatine kinase-myocardial band analyses that yielded a result suggestive of acute myocardial infarction increased from 27.2% to 45.5% (relative risk: 1.6, 95% CI: 1.5–1.8). The proportion of patient encounters where brain computed tomography scans were performed declined from 12.4% to 9.3% (relative risk: 0.75, 95% CI: 0.67–0.83), and the proportion of brain computed tomography scans that yielded abnormal results increased from 22.4% to 37.1% (relative risk: 1.6, 95% CI: 1.4–1.9). The proportion of patient encounters where amoxicillin clavulanic acid was prescribed declined from 79.5% to 54.6% (relative risk: 0.68, 95% CI: 0.67–0.69). <b><i>Discussion/Conclusions:</i></b> There was a reduction in the use of three unnecessary services following the implementation of CWC coupled with improved diagnostic yield. Based on these preliminary results, we recommend continuing with the CWC and conducting more robust studies to overcome the limitations of this current study and to assess the long-term effects of the CWC.