A Gram-positive, rod-shaped, endospore-forming organism, strain BL3-6$^T$, was isolated from tidal flat sediments of the Yellow Sea in the region of Tae-An. A 16S rRNA gene sequence analysis demonstrated that this isolate belongs to the Bacillus cereus group, and is closely related to Bacillus mycoides (99.0% similarity), Bacillus thuringiensis (99.0%), Bacillus weihenstephanensis (99.0%), Bacillus cereus (98.9%), Bacillus anthracis (98.8%), and Bacillus pseudomycoides (98.1%). The phylogenetic distance from any validly described Bacillus species outside the Bacillus cereus group was less than 95.6%. The DNA G+C content of the strain was 39.4 mol% and the major respiratory quinone was menaquinone-7. The major cellular fatty acids were iso-$C_{14:0}$ (17.8%), iso-$C_{16:0}$ (15.8%), and iso-$C_{12:0}$ (11.3%). The diagnostic amino acid of the cell wall was meso-diaminopimelic acid and the major cell wall sugar was galactose. The results of DNA-DNA hybridization (<55.6%) and physiological and biochemical tests allowed genotypic and phenotypic differentiation of strain BL3-6$^T$ from the published Bacillus species. BL3-6$^T$ therefore represents a new species, for which the name Bacillus gaemokensis sp. nov. is proposed, with the type strain BL3-6$^T$ (=KCTC 13318$^T$ =JCM 15801$^T$).