Chondrosarcoma (CS) is a malignant tumour of long and flat bone characterised by the formation of cartilage. Mesenchymal chondrosarcoma (MCS) is a rare subtype of CS that is more aggressive and may lead to erroneous diagnosis in a limited biopsy. The diagnosis is mainly based on the histopathological appearance of biphasic pattern of undifferentiated small round cells separated by islands of well-differentiated hyaline cartilage. We report a case of 13-year-old boy who initially presented with gum swelling and the biopsy result suggested a benign fibrous lesion. Following an extensive lesion shown in radiologic findings, the tumour excision was done and finally was diagnosed as an MCS of the maxilla. The patient was given postoperative chemotherapy (EURO-EWING 99 regimen), and now on regular follow-up for monitoring of local recurrence or tumour metastasis.