We report a simple method that uses proteins to solubilize single-walled carbon nanotubes (SWNTs) in water. Characterization by a variety of complementary techniques including UV-Vis spectroscopy, Raman spectroscopy, and atomic force microscopy confirmed the dispersion at the individual nanotube level. A variety of proteins differing in size and structure were used to generate individual nanotube solutions by this noncovalent functionalization procedure. Protein-mediated solubilization of nanotubes in water may be important for biomedical applications. This method of solubilization may also find use in approaches for controlling the assembly of nanostructures, and the wide variety of functional groups present on the adsorbed proteins may be used as orthogonal reactive handles for the functionalization of carbon nanotubes.