The CCN protein family is composed of six matricellular proteins, which serve regulatory roles rather than structural roles in the extracellular matrix. First identified as secreted proteins which are induced by oncogenes, the acronym CCN came from the names of the first three members: CYR61, CTGF, and NOV. All six members of the CCN family consist of four cysteine-rich modular domains. CCN proteins are known to regulate cell adhesion, proliferation, differentiation, and apoptosis. In addition, CCN proteins are associated with cardiovascular and skeletal development, injury repair, inflammation, and cancer. They function either through binding to integrin receptors or by regulating the expression and activity of growth factors and cytokines. Given their diverse roles related to the pathology of certain diseases such as fibrosis, arthritis, atherosclerosis, diabetic nephropathy, retinopathy, and cancer, there are many emerging studies targeting CCN protein signaling pathways in attempts to elucidate their potentials as therapeutic targets.