Background: The 2021 Centers of Disease Control and Prevention (CDC) sexually transmitted infection treatment guidelines recommend a 7-day course of metronidazole or single-dose tinidazole for women with trichomoniasis due to improved patient outcomes compared with single-dose metronidazole therapy. A health system antimicrobial stewardship program implemented an interruptive electronic health record (EHR) alert to promote optimal trichomoniasis prescribing when nonrecommended treatment is ordered. Objective: To determine the impact of an interruptive EHR alert on optimal trichomoniasis prescribing for women. Methods: This was an institutional review board–approved, single pretest, posttest quasi-experiment of women ≥15 years with a microbiologically confirmed Trichomonas vaginalis infection from 10/2023 to 12/2023 (preintervention) and 10/2024 to 12/2024 (postintervention). An EHR alert was implemented 9/2024 that notifies prescribers that single-dose metronidazole 2 g is not recommended and suggests CDC-recommended treatments. The primary outcome was the proportion of single-dose metronidazole 2 g orders before and after EHR alert implementation. A secondary cross-sectional evaluation of all alerts triggered from 10/2024 to 12/2024 was performed and included the number of alerts, location of alert, and provider response. Results: A total of 285 patients were included, 49.8% pre-intervention and 50.2% postintervention. Metronidazole 2 g was prescribed for 8.45% of pre-intervention and 2.80% of postintervention patients (P = 0.038). The clinical support alert fired 102 times for 75 patients during the 3-month postimplementation period. The alert was associated with a change in intended prescription to a metronidazole 7-day course in greater than 60% of patients over 3 months. Conclusion: The implementation of an interruptive alert was associated with high acceptance and improved prescribing for women treated for trichomoniasis.