Bi-component fibers typically combine multiple functions that arise from at least two distinct components. As a result, these fibers can incorporate carbon nanotubes, which impart specific and controllable mechanical, electrical, and thermal transport properties to the fibers. Using gel spinning, sheath-core polyacrylonitrile-polyacrylonitrile/carbon nanotube bi-component fibers with a diameter of less than 20 μm and carbon nanotube concentrations of up to 10 wt% were produced. In these fibers, the carbon nanotubes were well dispersed and aligned along the fiber axis. The fibers exhibited a tensile strength as high as 700 MPa, and a tensile modulus as high as 20 GPa, as well as enhanced electrical and thermal conductivities when compared to the fibers without carbon nanotubes.