Two Gram-negative, aerobic, motile, rod-shaped bacteria, designated strains 908033(T) and 908087(T), were isolated from a seawater sample collected from the East China Sea. Chemotaxonomic characteristics of the two isolates included the presence of iso-C(15 : 0), iso-C(17 : 0) and iso-C(17 : 1)omega9c as the major cellular fatty acids and Q-8 as the predominant ubiquinone. The genomic DNA G+C contents of strains 908033(T) and 908087(T) were 45.5 and 45.2 mol%, respectively. Phylogenetic analyses based on 16S rRNA gene sequences revealed that the new isolates were related to members of the genus Pseudidiomarina, showing levels of similarity of 95.8-96.6 % with the type strains of recognized species of the genus. The results of DNA-DNA hybridization experiments among these two isolates and Pseudidiomarina sediminum CICC 10319(T), in combination with chemotaxonomic and phenotypic data, demonstrated that the new isolates represent two novel species of the genus Pseudidiomarina, for which the names Pseudidiomarina donghaiensis sp. nov. (type strain 908033(T)=CGMCC 1.7284(T)=JCM 15533(T)) and Pseudidiomarina maritima sp. nov. (type strain 908087(T)=CGMCC 1.7285(T)=JCM 15534(T)) are proposed.