Thyroid disease is the most common endocrine system disease in animals. In this paper, the Traditional Chinese Veterinary Medicine (TCVM) etiology and treatment of the most common feline and canine thyroid diseases (hyperthyroidism, hypothyroidism) is presented. Feline hyperthyroidism is divided into 4 TCVM Patterns for diagnosis and treatment: Liver Qi Stagnation with Stagnation of Blood and Phlegm, Qi Deficiency (Spleen Qi), Qi-Yin Deficiency and Yin Deficiency with Liver Yang Floating. Treatment principles should include nourishing Yin, clearing Heat, relieving Stagnation and soothing Liver Qi. Canine hypothyroidism is divided into 3 TCVM Patterns for diagnosis and treatment: Liver Qi Stagnation, Qi-Yang Deficiency, and Qi-Yin Deficiency. The treatment principles should include tonifying pre-natal and post-natal Jing, soothing Liver and nourishing Yin. TCVM can be used as sole therapy for mild conditions in younger patients. For older animals or more severe cases, the use of both conventional treatment and TCVM is recommended. Benefits from adding TCVM therapy, even when using conventional treatment include: lowering medication doses to decrease adverse drug effects, restoring balance through addressing the TCVM root disorder, decreasing the development of other endocrinopathies or diseases and improved life quality for the animal.