To improve the bonding ability of artificial hair towards soft tissue, type I atelocollagen was immobilized onto the hair surface. The artificial hair used was made of a poly(ethylene terephthalate) monofilament. Following photo-induced graft polymerization of a hydrophilic monomer onto the surface of artificial hair, collagen was complexed with the graft chains. Poly(acrylic acid) was selected as the polymer to be grafted onto the artificial hair because this synthetic polymer exhibited the greatest ability to form an interpolymer complex in solution with collagen among the three anionic polymers poly(acrylic acid), poly(2-acrylamido methylpropane sulfonic acid), and sodium poly(styrene sulfonic acid). When the surface of the poly(ethylene terephthalate) film used as a model substrate was grafted with poly(acrylic acid), the surface density of the collagen immobilized by interpolymer complexation was found to increase with increasing surface density of the graft chains. Immobilization of collagen onto the filament surface was confirmed by surface analysis with X-ray photoelectron spectroscopy and transmission electron microscopy. It was shown that in vitro degradation of the collagen immobilized onto poly(ethylene terephthalate) was suppressed by crosslinking the collagen molecules with glutaraldehyde. Cell culture tests revealed that L-cells were attached well to the surface of collagen-immobilized artificial hair. The surface-modified hairs were implanted percutaneously in the scalp of a human volunteer. Neither infection nor rejection of the hair filaments was observed after 1 year of implantation. It was found that the number of collagen-immobilized filaments remaining fixed in the scalp after 3 years of implantation was significantly larger than that of untreated filaments. These results indicate that surface-modified artificial hair is highly biosafe and shows excellent tissue adhesion.