Ethical and regulatory guidelines recommend disclosure of medical errors to patients and families. Yet few studies examine how to effectively train healthcare professionals to deliver communications about adverse events to family members of affected pediatric patients. This pilot study uses a preintervention-postintervention study design to investigate the effects of medical error disclosure training in a simulated setting for pediatric oncology nurses (N=16). The results of a paired t test showed statistically significant increases in nurses' communication self-efficacy to carry out medical disclosure (t = 6.68, p < .001). Ratings of setting "realism" and simulation effectiveness were high (21 out of 25 composite score). Findings provide preliminary support for further research on simulation-based disclosure training for healthcare professionals.