We present transmission electron microscopy and Raman spectroscopy of amorphous carbon (a‐C) films deposited on clean surfaces of nickel (Ni) nanoparticles at room temperature. In the Raman spectrum measured from the a‐C film on the Ni nanoparticles, the broad peaks of the D and G modes appeared at 1388 and 1582 cm−1, respectively. The high‐resolution images and the corresponding filtered inverse fast Fourier transformed images of the a‐C film on the individual Ni nanoparticles showed that the a‐C film only around the Ni nanoparticles formed disordered graphitic layers, similar in structure to carbon black, without heat treatment. The present observation suggests that spontaneous graphitization of a‐C on the clean surfaces of the Ni nanoparticles occurs at room temperature. Copyright © 2016 John Wiley & Sons, Ltd.