In this report, we have identified the first Japanese family harboring the p.Val876Glu mutation in CACNA1S. Because only two families with HypoPP have been reported to carry this mutation, our data further strengthened the uniqueness of p.Val876Glu regarding its structural location in Cav1.1 and the clinical phenotype associated with the mutation (Ke et al., 2009; Yang et al., 2015). Here, CACNA1S is linked to hypokalemic periodic paralysis.