Background: Tetralogy of Fallot (TOF) is a congenital heart defect characterized by four anatomical abnormalities. Cardiac MRI has emerged as a valuable non-invasive imaging modality for comprehensive evaluation of cardiac structure and function. This study aimed to evaluate the role of magnetic resonance imaging in assessment of post Fallot tetralogy surgical repair. Methods: This observational study included 30 patients with repaired Tetralogy of Fallot and referred to diagnostic radiology department, at Benha University Hospitals. All patients were subjected to complete history taking, full clinical examination, 12 lead ECG, Echocardiography, and Cardiac MRI. For further evaluation of CMR parameters, the studied subjects were divided into two group according to RVEF: Group A were patients with RVEF 50%. Results: The mean age was 13.13 years. Sixty percent of the studied subjects were males and 40% were females. According to CMR parameters, RVEF mean level was 51.54. RV cardiac output mean level was 6.06 L/minute, RV stroke volume mean was 99.94%, RVEDV was 164.18 ml and RVESD mean was 75.87 ml. Pulmonary regurgitation fraction mean was 41.44, RV mass was 91.03 and LVEF mean was 69.25%. Conclusion: Cardiac MRI plays a crucial role in the assessment of post-surgical repair cases of Tetralogy of Fallot. By providing detailed anatomical and functional information, it helps clinicians evaluate the success of the surgical repair, detect residual abnormalities, and guide further interventions.