Three facultative psychrophilic Gram-positive bacterial strains were isolated from brine samples from the sea ice community in Antarctica. All strains were coccoid to rod-shaped and exhibited broad salinity and temperature ranges for growth. The three strains were subjected to 16S rDNA sequencing and subsequent phylogenetic analysis. All possess unique 16S rDNA sequences indicating they are new, previously unreported organisms. Phylogenetic analyses coupled with phenotypic characterization indicated that one of the strains is most closely related to the low mol% G + C genus Planococcus for which a new species, P. mcmeekinii, is proposed. The two other strains are members of the high mol% G + C Gram-positive bacteria and most closely related to the genera Arthrobacter and Brachybacterium. This study reports the first phylogenetic evidence that Gram-positive bacteria reside in the marine sea ice brine.