Patients with intellectual disability (ID) typically exhibit significant defects in both intelligence and adaptive behavior. Aberration of several genes involved in proper progression of mitosis has been reported to underlie ID. Here, we report a new patient with a novel mutation of CHAMP1.Whole exome sequencing (WES) analysis was performed. We isolated lymphoblast cells from the CHAMP1 patient and observed chromosome segregation.We identified a de novo frameshift mutation in CHAMP1. We find that these cells exhibit an increase in centrosome number and resulting multipolar spindle formation. The phenotypes observed in the patient's lymphoblastoid cells were presumably because of cytokinesis failure. We also confirm the identical phenotypes in human culture cells depleted of CHAMP1.CHAMP1 encodes a protein regulating kinetochore-microtubule attachment and chromosome segregation. These data strongly support that CHAMP1 mutations cause ID, and suggest that CHAMP1 is critical for progression of cytokinesis and maintenance of centrosome number.