Missed gland is an extremely rare condition. It is a mediastinal thyroid mass found after total thyroidectomy. We report a case of missed gland. The patient underwent total thyroidectomy due to multinodular goiter and thyroid stimulating hormone levels did not increase after surgery. Pathological tests revealed a micropapillary carcinoma. Thyroid ultrasonography and scintigraphy scan revealed mediastinal thyroid mass. The patient underwent redo surgery without sternotomy and there was no morbidity after the second surgical procedure. Most missed thyroid gland cases are due to incomplete removal of plunging thyroid goiter during total thyroidectomy. They also can be attributed to a concomitant, unrecognized mediastinal goiter, which is not connected to the thyroid gland with vessels or a thin fibrous band. It should be noted that absence of signs like mediastinal mass or tracheal deviation in preoperative chest X-ray does not exclude substernal goiter. The presence of a missed thyroid gland should be kept in mind when postoperative thyroid stimulating hormone levels remain unchanged.