Heart failure is a detrimental consequence of various cardiac diseases，and one of its pathological bases is the structural and functional changes caused by progressive interstitial fibrosis. Fibroblasts mediate and activate fibrosis to generate extracellular matrix，and excessive activation leads to the accumulation of matrix proteins，ultimately resulting in pathological fibrosis and organ damage. Thyroid hormone plays a crucial role in regulating the cardiovascular system，while subclinical and overt thyroid disorders impact cardiac fibrosis through a series of pathological mechanisms. Thyroid hormone replacement therapy is also considered for safeguarding cardiac function. This review is to provide an overview of current research on thyroid hormones and cardiac fibrosis.