We have successfully prepared highly c-axis oriented sol-gel derived LiNb1-xTaxO3 films on Si(lll) substrates. The orientations of LiNb1-xTaxO3 films for different values of the tantalum composition, x, are investigated Highly c-axis oriented films were obtained in the composition range of 0 < x < 0.33 and the degree of the orientation was found to be relatively low when 0.5 < x < 1. The c-axis orientation of the films is believed to result from a weak effect caused by the 3-fold symmetry match between the film and the Si(lll) substrate. C-axis oriented LiNb1-xTaxO3 films are very useful in integrated optical devices, pyroelectric devices, and metal-ferroelectric-semiconductor nonvolatile memory applications.