Two Gram-positive, rod-shaped, moderately halophilic bacteria were isolated from a deep-sea carbonate rock at a methane cold seep in Kuroshima Knoll, Japan. These bacteria, strains IS-Hb4^T and IS-Hb7^T, were spore-forming and non-motile. They were able to grow at temperatures as low as 9 °C and hydrostatic pressures up to 30 MPa. Based on high sequence similarity of their 16S rRNA genes to those of type strains of the genus Halobacillus, from 96.4 % (strain IS-Hb7^T to Halobacillus halophilus NCIMB 9251^T) to 99.4 % (strain IS-Hb4^T to Halobacillus dabanensis D-8^T), the strains were shown to belong to this genus. DNA–DNA relatedness values of 49.5 % and 1.0–33.0 %, respectively, were determined between strains IS-Hb4^T and IS-Hb7^T and between these strains and other Halobacillus type strains. Both strains showed the major menaquinone MK7 and l-orn–d-Asp cell-wall peptidoglycan type. Straight-chain C_{16 : 0}, unsaturated C_{16 : 1} ω7c alcohol and C_{18 : 1} ω7c and cyclopropane C_{19 : 0} cyc fatty acids were predominant in both strains. The DNA G+C contents of IS-Hb4^T and IS-Hb7^T were respectively 43.3 and 42.1 mol%. Physiological and biochemical analyses combined with DNA–DNA hybridization results allowed us to place strains IS-Hb4^T (=JCM 14154^T=DSM 18394^T) and IS-Hb7^T (=JCM 14155^T=DSM 18393^T) in the genus Halobacillus as the respective type strains of the novel species Halobacillus profundi sp. nov. and Halobacillus kuroshimensis sp. nov.