Diversity of zooplankton in aquatic ecosystems of the northeast of La Pampa (Argentina) with emphasis on new species registered for the province.The northeastern region of La Pampa province has a large number of heterogenic aquatic ecosystems; however, limnological studies of these ecosystems are scarce. The objective of this study is to describe the composition of the zooplankton of five water bodies and report the presence of six species not previously registered in the province. Between 2016 and 2017, samples were taken in two small, highly transparent subsaline lakes ("water holes") with rooted vegetation and in three sub-or hyposaline shallow lakes, without vegetation and with less transparency. Eight cladocerans, nine copepods, and 27 rotifers were recorded. In all cases, rotifers dominated in number of species and density, but the zooplankton communities of the water holes differed from those of the shallow lakes. The aquatic ecosystems studied are in a reduced geographic area, but their diversity was greater than that of larger areas of La Pampa, which may be due to the heterogeneity of the water bodies included in this study. Three copepods (Argyrodiaptomus bergi, Boeckella bergi, and Eucyclops neumani) and three rotifers (Euchlanis dilatata, Lecane closterocerca, and Plationus patulus) have been identified for the first time in La Pampa province. This study confirms that the distribution of A. bergi and E. neumani is wider than known so far, which was restricted to Brazil and the Paraná -del Plata basin, but the remaining zooplankton are species widely distributed in Argentina. Thus, the lack of information in La Pampa was due to the absence of previous investigations.