Background: The tendency of developing malignancy in patients with congenital heart defects has been well documented. Osteosarcoma and tetralogy of Fallot (TOF) have never been so far reported to happen in a single patient. Case Report: An 8.5-year-old boy with history of repaired tetralogy of Fallot (TOF) one year back presented with refractory leg pain most frequently at nights. CT scan, bone scan and bone biopsy of the proximal part of the left fibula revealed: high grade intramedullary osteogenic sarcoma (OS) of osteochondroblastic type. Conclusion: According to latest genetic studies TOF and OS don't share any common genetic background; it would be interesting for clinicians to have in mind such tendency between TOF and OS to investigate if they share any origin genetically or developmentally?