Osteosarcoma, although the most common malignant bone tumor in long bones, represents only 5-8% of head and neck tumors, making it uncommon for clinicians. Conventional biopsy techniques can complicate diagnosis due to varying tissue representation in surrounding areas. This article discusses a case involving a 19-year-old female who presented with facial swelling and a rapidly growing intraoral mass. Initial panoramic radiography showed localized radio-opacity and root resorption. Incisional biopsies initially suggested diagnoses of ossifying fibroma and fibrous hyperplasia, which did not align with the clinical presentation. Repeat excisional biopsy extending to the periosteum revealed findings consistent with chondroblastic and fibroblastic proliferation, including malignant osteoid and myxomatous stroma, confirming chondroblastic osteosarcoma. The patient subsequently underwent neo-adjuvant chemotherapy followed by surgical resection and radiotherapy. This case underscores the critical importance of timely and accurate diagnosis in osteosarcoma, as delays can significantly impact patient prognosis. The article emphasizes the lessons learned from such experiences in managing this challenging malignancy.