UNLABELLED: Free vascularized fibular transfer has become a standard procedure in upper extremity reconstruction after resection of osteogenic tumors. The authors present two rare pediatric cases of high-grade osteosarcoma resection of the proximal humerus. A free vascularized fibula autograft including the physis based on the anterior tibial artery and vein was used for reconstruction in a delayed (case 1) and immediate (case 2) approach. The main focus of the article is to describe the surgical technique, which is also presented in a series of intraoperative videos. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, V.