Fibronectin (FN) can bind to certain integrin receptors on the cell surface through short peptide sequences, thereby transmitting extracellular stimuli to intracellular effector molecules. FNDC4 plays a similar role due to the constitution of a type III FN domain, which is a binding site for DNA, heparin, or cell surface. It mainly functions as a signal transmitter after being cleaved and secreted as the extracellular N-terminal fibronectin type III domain (sFNDC4). Emerging studies have shown that FNDC4 plays crucial roles in numerous diseases and holds significant implications for guiding clinical treatment. This review aims to summarize the different roles and the latest advances of FNDC4 in the development of various diseases, in order to provide new ideas for clinical treatment.