Children with underlying cardiac defects represent the largest cohort of pediatric patients requiring oral anticoagulant therapy. This study aimed to determine how much pediatric cardiology nurses understood about warfarin therapy, given their role as patient educators. Surveys were sent to four Australian pediatric hospitals that provided inpatient cardiac services. Data are presented descriptively, with relationship between variables analyzed using linear regression analysis. Forty-one completed questionnaires were received from 94 registered nurses. The majority of nurses held an undergraduate degree in nursing and were classified as senior registered nurses. Nurses did not demonstrate a good understanding of warfarin therapy. Knowledge deficits were identified across a broad spectrum of areas, with only 30% of nurses reporting that they felt equipped to provide families with education regarding oral anticoagulant therapy. Nurses regularly provide patients with education regarding medication regimes; however, the effectiveness of that education is rarely evaluated. This study suggests that pediatric nurses working with patients who are often prescribed oral anticoagulant therapy have significant knowledge deficits about anticoagulant therapy. The impact of this lack of knowledge on the effectiveness of patient education has not been evaluated, but it is unlikely to be helpful.