TGFBIp, also known as keratoepithelin and βig-h3, is among the most abundant proteins in the human cornea and approximately 60% is associated with the insoluble fraction following extraction in sodium dodecyl sulfate (SDS) sample buffer. TGFBIp is of particular interest because a wide range of mutations causes amyloid or fuchsinophilic crystalloid deposits in the cornea leading to visual impairment. In the present study, we show that the SDS-insoluble fraction of TGFBIp from porcine and human corneas is covalently linked to the NC3 domain of type XII collagen in a TGFBIp:type XII collagen stoichiometric ratio of 2:1 via a reducible bond. Since type XII collagen is anchored to striated collagen fibers of the extracellular matrix, its interaction with TGFBIp is likely to provide anchoring for cells to the extracellular matrix through the integrin-binding capability of TGFBIp. Furthermore, the TGFBIp-type XII collagen molecule will affect our understanding of the molecular pathogenesis of the TGFBI-linked corneal dystrophies.