We investigated a hybrid nanostructure comprised of carbon nanotubes (CNTs) directly grown on polyacrylonitrile-based carbon fibers (PAN-CFs) for three-dimensional energy materials. The optimum growth conditions, such as catalyst loading time in electroless deposition and growth temperature in chemical vapor deposition were identified. The thorn bush-like structures of the multi-walled CNTs on CFs were evaluated by field emission transmission electron microscope and field emission scanning electron microscope. Raman spectra and attenuated total reflectance Fourier transform infrared spectroscopy were used to analyze the crystal and chemical structures of CNTs on CFs. Base on the results from four-point probe measurement, the sheet resistance dropped from 40 Omega/sq for PAN-CFs to less than 10 Omega/sq for CNTs-grown PAN-CFs. The obtained CNTs/PAN-CFs revealed the specific surface area of 64.4 m(2)/g with a pore volume of 0.18 cm(3)/g. Moreover, a sulfur electrode with the CNTs/PAN-CFs current collector exhibited higher electrochemical performance than that of the electrode with planar aluminum current collector.