Differentiated carcinoma of thyroid is regarded as one of those malignancies which if dealt at the right time lead to good survival and outcome but if the management is delayed then not only it can lead to loss of precious life but poses a surgical challenge in advanced cases. We are presenting an advanced carcinoma thyroid with thrombus extending to right atrium presenting with swelling in front of neck from 2 months, insidious in onset gradually progressive. swelling was more prominent over right side of face & right upper limb. During evaluation there was a lesion arising from right lobe of thyroid gland 10.6 x 5.7 x 5.2cms. Right internal jugular vein thrombosis and inferiorly thrombosis is extending into right brachiocephalic vein, superior vena cava (SVC) and right atrium. Even in the absence of malignant findings on cytology, the presence of a tumor thrombus in the thyroid vein or internal jugular vein is highly suggestive for malignancy. It is a significant discovery that raises strong suspicions about distant metastases.