An attempt was made to encapsulate nickel into the cavity of the carbon nanotubes, which were prepared by the pyrolytic carbon deposition on the nanochannels of anodic aluminum oxide film. For nickel loading, the MOCVD (metal organic chemical vapor deposition) method using nickelocene was applied to the carbon-coated nanochannels and then the nickel/carbon nanotube composites were liberated from the anodic oxide film by alkaline treatment. The resultant carbon nanotubes contained numerous numbers of NiO nanoribbons with about 4 nm thickness and 20 nm width. The length of the longest nanoribbon was about 800 nm. The crystal structure of the NiO nanoribbons was determined by using the electron diffraction technique. Furthermore, the mechanism of the nanoribbon formation was discussed in relation to the formation processes of the nickel/carbon nanotube composites.