Osteosarcoma is the most common primary malignancy of bone if we exclude the marrow-based malignancies such as myeloma, lymphoma, and leukemia. Osteosarcoma is the eighth most common form of childhood cancer, comprising 2.4% of all malignancies in pediatric patients, and approximately 20% of all primary bone cancers. The proximal fibula is a very rare site for osteosarcoma, and in Mayo series, reported incidence was only 2%. The purpose of this article is to report a very rare presentation of osteosarcoma in proximal fibula and to discuss the challenges in its surgical management. Proximal fibula osteosarcoma carries a good prognosis if sound oncological margins are achieved during the initial surgery. In addition, lateral soft tissue structures should be meticulously reconstructed to prevent post-operative knee instability and to ensure a good functional outcome.