The present work provides a first description of the zoeal stages of the Caridean prawns Campylonotus vagans, C. semistriatus and C. capensis Bate, 1888. Zoeal stages one and two were obtained from plankton catches during several expeditions in the Magellan region and the southwestern Atlantic Ocean, and first zoeae of C. vagans were confirmed with larvae hatched in a laboratory culture. Based on the results obtained, we concluded the morphological differences of the presence/absence of carapace spines, the shape of the somites, the telson and its number of posterolateral spines to serve as diagnostic features for the determination of campylonotid larvae. Morphological comparisons with larvae of the Pandalidae, Palaemonidae, and Oplophoridae suggest the Campylonotidae to be phylogenetically related to the Oplophoridae. Additionally, a key for identifying the zoeal stages of the Campylonotidae from the southernmost region of America is given in order to facilitate future ecological and life history studies.