A new species of the "glaciale" group of Austrodecus Hodgson, 1907, Austrodecus nausinoos sp. n., is described from specimens collected by "Huinay Fjordos" expeditions to the southern Chilean fjords in 2005, 2011 and 2013. Specific to the new species is the combination of the following morphological characters: six-articled ovigers, auxiliary claws, two spines on the first coxa of leg 1, and a spur at the tip of the long abdomen. In addition to the species description we give an update of Child's ( 1995) key to the glaciale group of Austrodecus including the new species.