Aurora-B and -C kinases are members of the Aurora serine/threonine kinase family of mitotic regulators. Aurora-B kinase is evolutionarily conserved from yeast to humans and has multiple functions in chromosome condensation, cohesion, biorientation and in cytokinesis. In contrast, Aurora-C kinase has only been found in mammals, is upregulated in some tumor cell lines and tissues, and has a unique physiological role in spermiogenesis. Despite these known functions, little is known about the function of Aurora-C in mitosis. We have found that Aurora-C interacts with Borealin in addition to the other known members of the Aurora-B chromosomal passenger complex (CPC). We have also found that Aurora-C, like Aurora-B, phosphorylates the centromeric histone Centromere Protein-A (CENP-A) and Borealin in vitro. These molecular mechanisms are consistent with our observation that in the absence of Aurora-B, Aurora-C is sufficient for proper mitotic phosphorylation of CENP-A and centromeric localization of the CPC proteins. Thus, Aurora-C shares Aurora-B substrates and is capable of performing mitotic functions previously attributed only to Aurora-B.