Phenotypic and phylogenetic studies were performed on unidentified Gram-negative staining, haloalkaliphilic aerobe and protease producer Salinivibrio-like organism recovered from a saltish spring with algal mat in the “Pozzo del Sale” site (Salt's Well) in the Campania Region (South Italy). Phylogenetic analysis based on comparison of 16S rRNA gene sequences demonstrated that the isolate was related to species of Salinivibrio genus. The DNA–DNA hybridization of the type strain 18AG T with the most related Salinivibrio costicola subsp. costicola showed a re-association value of 72%. Based on the phenotypic distinctiveness of 18AG T strain and molecular, chemical and genetic evidence, it is proposed that strain 18AG T can be classified as S. costicola subsp. alcaliphilus, subsp. nov. The type strain of S. costicola subsp. alcaliphilus, is ATCC BAA-952 T ; DSM 16359 T .