Of the three species of hippolytid shrimps known to occur in the southwestern Atlantic Ocean, Nauticaris magellanica is the only representative of its genus. Zoeal larvae of N. magellanica were obtained from plankton samples taken by means of a plankton net in Argentine waters in the southwestern Atlantic Ocean during two expeditions carried out from onboard the RV Walther Herwig and the RV Shinkai Maru in 1978 and 1979, respectively. In the present work we distinguish and redescribe six zoeal stages of N. magellanica and compare our results with the previous description of larvae reared under laboratory conditions from a population off central southern Chile. Differences in size, number of setae on the appendages as well as in the development of the pereiopods are discussed from an ecological and biogeographical point of view.