Background: Firearm violence is the leading cause of death among US children and adolescents, and school nurses are increasingly recognized as key partners in prevention efforts. While school nurses are uniquely positioned to counsel on firearm safety, existing training curricula often lack content tailored to their specific roles and settings. Methods: We adapted a hospital-based curriculum for school nurses, comprising a didactic session on firearm violence, secure storage, and counseling frameworks, followed by standardized patient simulations. The pilot was conducted at a single academic medical center, and qualitative survey data were collected. The program's feasibility, acceptability, and efficacy were assessed using a pretest--posttest design. Results: Thirty school nurses participated, with 43.3% having prior firearm safety training and 10.0% trained to counsel on firearm safety. Post-training, confidence in counseling increased, particularly in discussing Extreme Risk Protection Orders and asking about the 5 Ls (locked, loaded, little children, low mood, and learned household members). Perceptions of the importance of screening and counseling also improved, while concerns about interference with student encounters decreased. Implications for School Health Policy, Practice, and Equity: By equipping school nurses with trauma-informed, proactive violence prevention tools, this curriculum expands their role as trusted, frontline leaders in creating safe, supportive environments. When embedded within holistic frameworks, school nurse-led efforts can help ensure all students thrive. Conclusion: This pilot training enhanced school nurses' confidence and perceptions of firearm safety counseling, setting the stage for efforts to expand its reach to additional locations and participants.