Focal or diffusely increased 18F-fluorodeoxyglucose (18FDG) uptake in thyroid gland are occasionally seen during 18FDG positron emission tomography (PET) scanning. Increased 18FDG uptake in thyroid nodules may be associated with benign or malignant tumours. In our case who was diagnosed as malignant melanoma, focally increased 18FDG uptake in a thyroid nodule was noticed. Thus, fine needle aspiration biopsy of the thyroid nodule was performed. On suspicious findings for the thyroid papillary cancer were reported, total thyroidectomy was performed. Histopathological evaluation revealed the thyroid papillary carcinoma. So, therapy for the incidental thyroid papillary carcinoma was commenced in this case who was under the follow-up for the malignant melanoma.