Inaccurate documentation of penicillin (PCN) allergies is a widespread issue that contributes to the overuse of broad-spectrum antibiotics, increased healthcare costs, and suboptimal patient outcomes. Many patients labeled as allergic to PCN are not truly allergic, leading to unnecessary avoidance of first-line therapies. Accurate allergy assessment is a critical component of antimicrobial stewardship efforts. This quality improvement project employed a pre- and post-intervention design to enhance nursing assessment of PCN allergies using the internationally validated PEN-FAST stratification tool. The purpose of this project was to reduce the inaccurate labeling of PCN-allergies. Registered nurses (RNs) received education on the PEN-FAST tool to improve their ability to assess the severity of PCN allergies and guide documentation in the electronic medical record (EMR). Three aggregated case studies were presented to participants pre-intervention and post-intervention, describing patients with different medical histories, symptoms, and PCN allergies. The intervention included training on the use of the PEN-FAST tool to differentiate between “low risk”, “moderate risk”, and “high-risk” patients with PCN allergies. The post-intervention results indicated statistically significant improvements in RN’s ability to assess PCN allergies using the PEN-FAST tool (p=.001, chi-square). RN's attitudes, knowledge, and assessment practices were evaluated using pre- and post-questionnaires. However, the first four survey questions related to PCN assessments and attitudes did not achieve statistical significance; the fifth survey question assessing RN trust in EMR allergy documentation demonstrated a significant decrease in trust levels among RNs post-intervention, which was statistically significant (p = .009, t-test). A descriptive analysis of the site-facility PCN assessment of current practice yielded mixed results. However, the PCN assessment survey responses indicated strong consistency with baseline PCN knowledge (86%–97%). The project enhanced RNs’ decision-making and assessment accuracy, enabling stratification of patients into “low-risk” and “high-risk” PCN allergy categories using the PEN-FAST tool. Utilizing a PCN-internationally validated tool can help reduce inaccurate labeling of PCN-allergic patients.