Intra-pericardial heterotopic thyroid (IPHT) is an incidental finding during open-heart surgery. Although heterotopic thyroid has been reported in different parts of the body, only a few cases of intra-pericardium have been reported so far. In most articles, intracardiac, intrathoracic and heterotopic thymus cases are mistakenly included as IPTH cases A 57-year-old man with a history of non-Hodgkin lymphoma, who was treated 8 years ago and recovered, is now a candidate for surgery due to clear cell renal carcinoma in the left kidney with inferior vena cava (IVC) thrombus tumor that has spread into the right atrium. At the same time, he was operated on by two teams of urology and heart surgery. The patient’s kidney was removed, and then he was subjected to sternotomy by the heart surgery team to remove the thrombus tumor. After opening the pericardium inside the pericardial cavity, a pericardial mass measuring 1×2 ×3 cm, which was connected to the lower surface of the aortic arch by a 1 cm long stalk, was observed. It was resected and sent to pathology laboratory. The rest of the surgery to remove the thrombus tumor from inside the right atrium and IVC continued according to the procedure. The pathological report was benign thyroid tissue. Actual cases of IPTH are underreported, and due to the small number, it is not yet possible to comment on the prevalence of malignancy in it or its functional role; However any lesion or abnormal mass in the pericardial cavity should be respected and sent to pathology laboratory therefore by collecting information about these masses, in the future, decisions can be made and summarized.