This is a prospective before-after study comparing peripheral intravenous cannulation (PIVC) placement and usage rates following a 10 week long multimodal intervention provided to medical and nursing staff working in a tertiary emergency department (ED). The intervention focused on improving appropriate use of PIVCs in an emergency setting by emphasizing to clinicians that a PIVC should only be placed if it was believed there was more than an 80% chance that it would be used. Patients were eligible for the study if they presented to the ED and were >18 years of age. Patients were excluded from the study if they were triage category 1, already had a PIVC placed in an ambulance, or were transferred from another hospital. Among the 4172 patients included in the analysis, there was a 9.8% reduction in the number of PIVCs inserted (95% CI 6.8-12.87) and a 12% increase in PIVC usage (95% CI 8.7-17.0%) in the post-intervention cohort. This article is protected by copyright. All rights reserved.