Species of dinophycean Amphidomataceae are producers of phycotoxins classified as azaspiracids. We provide the first records of two of their constituent species, Amphidoma languida and Azadinium dexteroporum, for the Irminger Sea off Iceland. Morphological examination and molecular characterization, including uncorrected mean pairwise distances between sequences of the Internal Transcribed Spacer (ITS), doubtlessly assigned the sub-Arctic strain 2A11 to the reference of Amphidoma languida. Strain 2A11 produced AZA-38 and AZA-39, corresponding to the toxin profile described for the type material. The sub-Arctic isolate 1D12 differed significantly in terms of ITS genetic distance (p = 0.04) from a Mediterranean Azadinium dexteroporum strain, but our morphological analysis did not reveal any major or stable diagnostic traits between the reference strain of Azadinium dexteroporum and the new strain described here. In contrast to the Mediterranean strain of Azadinium dexteroporum, the sub-Arctic strain 1D12 did not produce any known azaspiracids. The new records of Amphidoma languida and Azadinium dexteroporum from the Irminger Sea imply an important range extension of the species, formerly known from the northern and eastern Atlantic (Amphidoma languida) and from the Mediterranean area (Azadinium dexteroporum) only. Together with three new species of Azadinium recently described from the same expedition, the results clearly show that the biodiversity of the Amphidomataceae in the sub-Arctic is remarkably large.