A yellow-pigmented, Gram-negative, aerobic bacterial strain comprising rod-shaped cells devoid of flagellar and gliding motility, designated strain JC2129(T), was isolated from tidal flat sediment of Dongmak on Ganghwa Island, South Korea. Results from a 16S rRNA gene sequence analysis indicated that the isolate belonged to the family Flavobacteriaceae; the highest level of nucleotide sequence similarity (91.9%) occurred with Polaribacter dokdonensis DSW-5(T). The predominant cellular fatty acids were iso-C(15:0) (19.8%), iso-C(15:1) G (14.0%), iso-C(17:0) 3-OH (13.7%) and iso-C(13:0) (6.4%). Flexirubin-type pigments were absent. The major isoprenoid quinone was MK-6. The DNA G+C content was 43-45 mol%. Data from a polyphasic taxonomy study suggested that the isolate represents a novel genus and species in the family Flavobacteriaceae, for which the name Actibacter sediminis gen. nov., sp. nov. is proposed. The type strain of Actibacter sediminis is JC2129(T) (=KCTC 12704(T) =JCM 14002(T)).