This dataset provides nitrogen isotopic composition (δ¹⁵N) and total nitrogen (TN) measurements from marine sediment core SSD004 GC11 in the southern Arabian Sea covering the last ~167 ka. The records document variability in water-column denitrification, an important control on marine nitrogen cycling and atmospheric N₂O emissions. δ¹⁵N values indicate strong coupling between primary productivity and denitrification during warm intervals, with weaker coupling during cold periods despite continued productivity linked to winter monsoon mixing.