We used both nuclear ribosomal genes (28S rDNA, 18S rDNA, 5.8S rDNA, internal transcribed spacer regions: ITS1, ITS2) and mitochondrial CO1 sequences to group or distinguish morphotypes of Parafavella, a problematic genus of tintinnid ciliates of the marine microzooplankton. We sequenced 30 single cells of Parafavella from the Bering Sea, the Greenland Sea, and the East/Japan Sea. Sequences were obtained from 4 morphotypes, typically ascribed to P. gigantea, P. greenlandica, P. jorgenseni, and P. subrotundata and from GenBank, the nuclear ribosomal genes of P. parumdentata were retrieved. Cells of the 5 morphotypes had identical 18S and 5.8S gene sequences. ITS1, ITS2 and 28S sequences produced two clusters: one grouping P. greenlandica and P. parumdentata and the other grouping P. jorgenseni, P. gigantea, and P. subrotundata. In contrast, CO1 nucleotide data yielded eight haplotypes clustered into five groups: one composed of P. greenlandica morphotypes, two distinct haplotypes of P. jorgenseni, and two distinct haplotypes of P. gigantea with one including P. subrotundata morphotypes. We investigated the co-occurrence of different morphotypes in samples from sites across a large gradient of latitude and concentrations of Parafavella cells. Natural communities contained 2-6 different morphotypes. We conclude that both the crypticity within morphotypes and species polymorphism characterize Parafavella, as known for other tintinnid genera.