Riedel's thyroiditis is a very rare inflammatory condition. It affects not only the thyroid gland but also the adjacent vital structures. It may also be associated with different forms of systemic fibrotic disorders. The exact etiology is unknown, but currently, the most favorable opinion is that it is a localized form of the systemic fibrotic process. We report the case of a 38-year-old woman, presented with a 10-month history of progressive hypothyroidism, dysphonia, and dysphagia. A Doppler ultrasound study revealed massive thyroid enlargement with multiple Eu TIRADS 3 and 4 nodules. Fine needle aspiration was noncontributive on two occasions. A hard subtotal thyroidectomy was performed. Pathological study confirmed Riedel's thyroiditis with the presence of IgG4 antibodies in immunohistochemistry. The patient was successfully treated with levothyroxine replacement and corticosteroid therapy with rapid resolution of obstructive symptoms. The case descriptions highlight the diagnostic challenge of this disease, describe the response to surgical management and corticosteroid therapy, and give a short review of the subject.