Strain pht-3B(T) was isolated from a pyrene-degrading consortium of an enriched sediment from the Pacific Ocean, collected during the screening of polycyclic aromatic hydrocarbon-degrading bacteria. Cells were Gram-negative, short rods that were motile by means of flagella. Growth was observed at 0-7 % NaCl and 10-41 °C. The isolate was able to reduce nitrate to nitrite, but not to nitrogen. 16S rRNA gene sequence comparisons showed that strain pht-3B(T) was most closely related to Nitratireductor aquibiodomus NL21(T) (97.3 % 16S rRNA gene sequence similarity), N. indicus C115(T) (97.1 %), N. basaltis J3(T) (96.8 %) and N. kimnyeongensis KY 101(T) (96.7 %). DNA-DNA hybridization between strain pht-3B(T) and these reference strains revealed 55, 54, 28 and 42 % DNA-DNA relatedness, respectively. The dominant fatty acids were C(19 : 0)ω8c cyclo (22.6 %) and summed feature 8 (consisting of C(18 : 1)ω7c and/or C(18 : 1)ω6c; 60.4 %). The G+C content of the chromosomal DNA was 63 mol%. These characteristics were in good agreement with those of members of the genus Nitratireductor. According to cell morphology, physiology, fatty acid composition, 16S rRNA gene sequence analysis and DNA-DNA relatedness, the isolate belonged to the genus Nitratireductor but could be readily distinguished from recognized species of the genus. Therefore a novel species is proposed to accommodate strain pht-3B(T), for which the name Nitratireductor pacificus sp. nov. is proposed. The type strain is pht-3B(T) ( = CCTCC AB 209302(T) = LMG 25541(T) = MCCC 1A01024(T)).