Background: Metallic susceptibility artifact (MSA) on brain MRI has been described rarely in adult population as an incidental finding in patients undergone cardiac surgery, catheterization or prosthetic heart valve, but has not been described before in the pediatric population. Here we present two pediatric cases with MSA on brain MRI post-cardiac surgery. Case Series:Patient1: 13-month-old girl with Transposition of great arteries, aortic coarctation and multiple VSDs, who twice had open heart surgery requiring cardiac bypass. She presented with bilateral lower extremity paralysis secondary to spinal cord embolic infarction, Brain MRI showed an incidental finding of hundreds of diffuse foci of brain MSA. Patient2: 5-year-old boy with Trisomy21, Atrial-ventricular septal defect repaired at age one year. His brain MRI showed incidental finding of multiple, widespread foci of MSA during investigation for gait disturbance. Discussion: Here we present two pediatric patients post-cardiac surgery, found to have multiple scattered MSA in cerebral and cerebellar hemispheres and brain stem. Presumably, these are secondary to metallic microthrombi during cardiac surgery, however, neither had prosthetic material. Metallic microthrombi may be related to cardio-pulmonary bypass. Pediatric cardiac surgery patients should be studied, to understand the significance of these lesions and further distinguish the cause and association of these findings.