Abstract Dinophysis tripos ( Gourret, 1883) exhibits marked morphological variability and its small and intermediate forms may get confused with those of Dinophysis caudata when their blooms co-occur. D. tripos has been included in the list of toxin-producing Dinophysis spp. based on one single analysis by liquid chromatography with fluorescence detection (LC–FLD). After many years of absence, a D. tripos bloom occurred in the Galician Rias Baixas that was not associated with harvesting closures. Morphological, toxicological and genetic characteristics of D. tripos were described from cultures fed with the ciliate Myrionecta rubra grown on a cryptophyte ( Teleaulax amphioxeia). Toxin analyses (LC–MS) of plankton concentrates rich in D. tripos and cultures of the same species confirmed the presence of pectenotoxin-2 (PTX-2). Small and intermediate forms of D. tripos appeared in culture and allowed a good description of morphological features that differentiate them from those of D. caudata/Dinophysis diegensis. Phylogenetic analyses based on the ITS/5.8S rDNA region placed D. tripos in a subclade including D. caudata, Dinophysis fortii and Dinophysis infundibulus. Identical ITS/5.8S rDNA sequences were obtained for normal and small cells of D. tripos. This is the first report of the presence of PTX2 in D. tripos and of the establishment of mixotrophic cultures of this species.