A novel Gram-negative, aerobic, moderate halophilic, and psychrotolerant bacterium, designated as strain H7$^T$, was isolated from a hypersaline lake located in Skarvsnes, Antarctica. Cells were filaments with varying lengths. Coccoid bodies developed in old cultures. Growth occurred with 0.5-15% (w/v) NaCl (optimum, 5.8-7.0%), at pH 6.0-10.0 (optimum, pH 7.0-8.0), and at 10-28$^{circ}C$ (optimum, 25$^{circ}C$). The strain had a G+C content of 34.9 mol%, which is within the range of 32-36 mol% reported for the genus Psychroflexus. Chemotaxonomic data (major respiratory quinone: MK-6; major fatty acids: $aC_{15:0}$, $iC_{16:0}$ 3-OH, and $aC_{15:1}$ A) supported the classification of strain H7$^T$ within the genus Psychroflexus. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain H7$^T$ should be assigned to the genus Psychroflexus and has a homology with Psychroflexus salinarum (98.2%), P. sediminis (96.1%), P. torquis (95.2%), P. tropicus (95.8%), and P. gondwanense (92.2%). Strain H7 is not identified as P. salinarum because that DNA-DNA hybridization data were 8.5% between strain H7$^T$ and P. salinarum. The combination of phylogenetic analysis, DNA-DNA hybridization data, phenotypic characteristics, and chemotaxonomic differences supported the view that strain H7$^T$ represents a novel species of the genus Psychroflexus. The name Psychroflexus lacisalsi is proposed, and the type strain is H7$^T$ (=JCM 16231$^T$ =KACC 14089$^T$).