Introduction: Voriconazole (VRCZ) is a triazole antifungal agent for which therapeutic drug monitoring (TDM) is recommended. At Juntendo University Hospital, the VRCZ TDM implementation rate was 42% between January 2011 and October 2017. Here, we report that modifications to the hospital’s drug ordering system improved the implementation rate of VRCZ TDM.Method: In August 2018, the drug ordering system was modified so that a message appeared on the screen to notify clinicians of the need to monitor VRCZ blood concentrations and to recommend a date for sample collection. In addition, the laboratory orders for VRCZ levels were digitized. We compared two one-year periods before and after implementation of the modifications (August 2017 to July 2018 and August 2018 to July 2019) to verify the effect of the changes.Result: Results showed an increase in the TDM implementation rate: 12 patients (42.8%) received TDM before modification of the system, and 26 patients (92.9%) received TDM after modification of the system. Further, the rate of blood sampling at the recommended time point for estimating blood concentration (day 5-7 after the start of administration) improved after system modification, i.e., blood samples were collected from 18 patients (64.3%) at the steady state point. In contrast, blood samples were collected from only 6 patients (21.4%) before system modification. When blood concentrations deviated from the target range in patients who received TDM, clinicians took appropriate actions, such as reducing drug doses, prescribing drug holidays, or discontinuing medications.Conclusion: A system that provides information related to VRCZ blood concentration measurements can help clinicians provide patients with optimal pharmacotherapy.