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. The new δ¹⁵N record is combined with published regional datasets to produce a basin-wide Arabian Sea denitrification stack. Spectral and cross-wavelet analyses reveal dominant orbital-scale variability, with stronger obliquity influence in the southern basin and precession dominance in northern records. Coherent variability between δ¹⁵N records and atmospheric N₂O concentrations highlights orbital forcing as a key driver of long-term nitrogen cycling and greenhouse gas variability.