In this study we analyzed eukaryotic phytoplankton diversity and community composition based on sequencing the 18S rRNA gene in three little known frontal areas of the Argentine Sea. Sampling was carried out in early austral summer on the R/V Bernardo Houssay from January 6th to 12th 2016, along three study areas covering a latitudinal gradient: a) Stations 1-2 located in front of Valdés Peninsula (˜43°S), b) Stations 7, 8, 9 located in front of the southern tip of San Jorge Gulf, i.e. Blanco Cape (˜47°S), and c) Stations 15-16 located in front of de los Estados Island (˜55°S).