Human chromosome 15q11–q13 is subject to regulation by genomic imprinting, an epigenetic process by which genes are expressed in a parent-of-origin specific manner. Three neurodevelopmental disorders, Prader–Willi syndrome, Angelman syndrome, and 15q duplication syndrome, result from aberrant expression of imprinted genes in this region. Here, we review the current literature pertaining to mouse models and recently identified patients with atypical deletions, which shed light on the epigenetic regulation of the chromosome 15q11–q13 subregion and the genes that are responsible for the phenotypic outcomes of these disorders.