A proteomic study predicted that about one hundred kinds of proteins constitute a basic structure of the centrosome. Most of the core centrosomal proteins contain extensive coiled-coil domains, suggesting that the protein-protein interaction is a critical force for the core centrosome configuration. In the present study, we investigated a novel interaction between CEP135 and C-NAP1, two core centriolar proteins. Depletion of CEP135 caused a premature centrosome splitting. Reduction of the centrosomal C-NAP1 level was accompanied in a specific manner. Ectopic expression of the CEP135 mutant proteins also caused centrosome splitting in association with the reduction of the centrosomal C-NAP1 levels. Based on these results, we propose that CEP135 acts as a platform protein for C-NAP1 at the centriole.