Introduction: Primary malignant melanoma of the oral cavity is a rare neoplasm. The tumors tend to metastasize or locally invade tissue more readily than other malignant tumors in the oral region. Case Report: A 55 year old male presented with left sided hard cervical lymphadenopathy with unknown primary with cytology of malignant melanoma. 18FDG-PET-C.T scan helped identification of the primary. Discussion: The survival of patients with mucosal melanomas is less than for those with cutaneous melanomas. Tumor size and metastases are related to the prognosis of the disease. Early oral malignant melanomas can be clinically very difficult to distinguish from other benign oral pigmented lesions. Conclusion:  Any case presenting with cervical lymphadenopathy with a cytological diagnosis of Malignant Melanoma and without clinically identifiable primary, early detection using whole body 18FDG-PET CT is utmost important.