Blastobasis tarda is a moth of the family Blastobasidae. It is found in Australia in Queensland and New South Wales, as well as New Zealand. It is an introduced species in North America, where it has been found in southern California. It has also been reported from France. The wingspan is about 15 mm. Adults have brown forewings with fringes along the inner margin that are longer than the width of the rest of the wing. The hindwings are paler and narrower and have fringes along the costa and even longer ones along the inner margin. Adults are sexually dimorphic.