The assemblages of diatoms contained in nineteen surface sediment samples recovered off the coast of Málaga province (Spain) between 5°W and 4°38′W have been analysed. The variations observed in the diatom assemblage point to the presence of nutrient-enriched waters, transported laterally from the centre of an upwelling that occurs to the west of the study area. The utility of species such as Paralia sulcata, Thalassionema nitzschioides and the spores of Chaetoceros spp. in the reconstruction of physico-chemical and biological characteristics and of the spatial structure of the upwelling is confirmed.