Riedel's thyroiditis is a rare entity consisting of a fibrotic process of the thyroid which can generate gland destruction, infiltration of cervical structures and even airway obstruction. It has been associated with systemic fibrotic disorders, autoimmune diseases, and more recently with spectrum of diseases related to excess of Immunoglobulin G type 4 (IgG4). Two cases of Riedel's thyroiditis by IgG4, confirmed by immunohistochemistry and was managed surgically with favorable results during the follow-up time, are presented. These case descriptions highlight the diagnostic challenge of this disease, describe the response with surgical management, and make a brief update on the subject.