Two decapod crustacean larval morphotypes belonging to the Anomura and Brachyura were found for the first time in Antarctic waters. Nine specimens were obtained from qualitative plankton hauls in the Maxwell Bay (Bransfield Strait) (62°14Ž33 S; 58°43Ž81 W) off King George Island, Antarctic Peninsula. The anomuran morphotype belonged to the Hippidae, and apparently to the genus Emerita, whereas the brachyuran representative was assigned to the genus Pinnotheres (Pinnotheridae). At present species determination is not possible due to lack of knowledge of larval morphology in both families. Adult forms of these reptant decapods are not known from Antarctic waters, the occurrence of the present larval forms is considered as a possible intrusion of Subantarctic water masses into the Antarctic environment. This hypothesis is supported by the additional presence of the copepod genus Acartia in the same sample material, which is exclusively known from Subantarctic waters.