Three bacterial strains producing blue-violet pigmented colonies on R2A agar were isolated from a wet rock wall and lakes in a deglaciated northern part of James Ross Island, Antarctica. The isolated strains inhibited phytopathogenic Gram-positive bacteria, e.g. Clavibacter spp., Curtobacterium flacumfaciens, and Paenarthrobacter ilicis. Phylogenetic analysis based on the 16S rRNA gene indicated that the isolates belonged to the genus Massilia and the closest relatives were Massilia violaceinigra B2T, Massilia rubra CCM 8692T, Massilia frigida CCM 8695T, Massilia antarctica CCM 8941T, and Massilia aquatica CCM 8693T. A polyphasic taxonomic study based on lepA genes sequencing, automated ribotyping, MALDI-TOF MS, chemotaxonomy analyses, extensive biotyping, average nucleotide identity, and digital DNA-DNA hybridization calculations based on whole-genome sequences proved that the isolates represent a novel Massilia species for which the names Massilia pseudviolaceinigra sp. nov. and Massilia scottii sp. nov. are suggested, with the type strains P3689T (= CCM 9206T) and P5043T (= CCM 9029T), respectively. These two bioactive-substances-producing species may play an important role in shaping the composition of fresh-water Antarctic microbiomes due to the inhibition of various Gram-positive bacteria.