Diffuse lipomatosis of thyroid gland is very rare disease, characterized by diffuse proliferation of adipose tissue in the thyroid gland, the pathophysiology of adipose tissue infiltration in the thyroid gland remains unknown. We report a case of a 55-year-old female who presented 6 months ago a dysphonia, ultrasound of the neck revealed the presence diffuse goiter with heterogeneous echogenicity, her thyroid hormone levels were normal, thyroid isotope scanning showed heterogeneous uptake of radioactivity and coexistence of cold and hot nodules. The patient underwent total thyroidectomy. Histological study concluded to the diagnosis of diffuse lipomatosis of thyroid gland.