Leucism is a partial hypopigmentary congenital disorder previously recorded in several species of mammals. This abnormal coloration is unusual in the wild. In August 2013, in Baja California, México, we collected 2 Peromyscus fraterculus (one female and one male) exhibiting leucism. Leucism has not been previously reported in the genus Peromyscus; therefore, we documented the first known record. Leucism is expressed in natural populations having low genetic diversity and may increase selective pressure on affected individuals.