The grain-size effect on the preferred orientation has been revealed in TiC/alpha-C:H nanocomposite films grown by magnetron sputtering, in which the grain size of TiC can be adjusted through changing C content in films. The finding is that the preferred orientation of films is significantly affected by the grain size, and the crystallographic orientation changes from face-centered cubic (fcc) TiC(1 1 1) to (2 0 0) as the grain size of nanocrystallite TiC decreases from similar to 22.3 to similar to 4.7 nm. This size-dependent preferred orientation is explained via thermodynamic calculations, from which the size-dependent Gibbs free energies are found to be a key factor that controls the texture development in thin films if the grain size in films is sufficient small. Crown Copyright (C) 2012 Published by Elsevier B. V. All rights reserved.