The BRCA2 gene is involved in recombinational DNA repair and cytokinesis. BRCA2 defects are associated with chromosomal abnormalities, which is a hallmark of genomic instability that contributes to tumorigenesis. Here, we show that downregulation of a BRCA2 interacting protein (BCCIP) in HT1080 cells leads to chromosomal polyploidization, centrosome amplification and abnormal mitotic spindle formation. The BCCIP knockdown cells can enter mitosis and retain spindle checkpoint, but fail to complete cytokinesis. Our data suggest an essential role of BCCIP in the maintenance of genomic integrity.