Background: Early ambulation is a effective and safe intervention to reduce complications of immobility for pediatrics post-cardiac catheterization. Aim: The research evaluated the effect of upgrading nurses’ performance regarding early ambulation and health outcomes of pediatrics with congenital heart defects following cardiac catheterization. Research design: A quasi-experiment. Setting: At the cardiology unit at Beni-Suef University Hospital. Subjects: included a convenient sample of thirty nurses and a purposeful sample of fifty children before and after the program. Tools: Four tools were used to gather data: an Arabic interview questionnaire to assess the study participants' understanding of early ambulation, an observational checklist to assess the nurses' early ambulation practices, and a 5-point Likert scale of attitudes. Results: Compared to pre- and post-program implementation, there was a significant improvement in overall knowledge, practice, and attitude, as indicated by the following percentages: (26.6% to 83.3%), (16.6% to 76.7%), and (10.0% to 80.0%), respectively. Furthermore, compared to the preprogrammed, the educational program improved the health outcomes for children with congenital heart defects after cardiac catheterization. In conclusion, introducing an educational program improved children's health outcomes and nurses' knowledge, practice, and attitude. Recommendation: It is suggested that nurses be more aware of the advantages of early ambulation following cardiac catheterization and how to prevent complications by providing in-service training sessions.