In breast-conserving surgery, an optical wire is a useful surgical guiding tool to optically locate small lesions within the breast tissue. However, the use of a long silica glass fiber as the optical wire can be burdensome to patients because of its stiffness and nonbiocompatibility. We investigate the use of a biocompatible fiber for light localization in tissue. A surgical suture with a diameter of 400 μm and a few centimeters long is employed as the biocompatible optical waveguide to transport the visible laser light to the inner tissue site. Optical location is confirmed with glow ball-like red laser illumination at the tip of the suture embedded within a fresh chicken breast tissue. Effective optical power coupling to the suture is made by using a double-cladding fiber coupler. From this preliminary result, we realize practical light localization with biopolymer waveguides.