This dataset presents stable oxygen isotope ratios measured on the epibenthic foraminifera Cibicidoides wuellerstorfi and Cibicides kullenbergi at International Ocean Discovery Program Site U1540 (55° 8.47ʹ S, 114° 50.52ʹ W, 3580 m) during Marine Isotope Stage 11. Full replicates were conducted to determine the 1σ-uncertainty of the analyses. The results are expressed in delta-notation (δ¹⁸O) with reference to the Vienna Pee Dee Belemnite (VPDB) standard and were corrected by +0.64 ‰ VPDB to account for disequilibrium effects. The samples were measured with a Thermo Fisher Scientific MAT 253 isotope ratio mass spectrometer coupled to a Kiel IV carbonate preparation device at the Leibniz Laboratory for Radiometric Dating and Stable Isotope Research at Kiel University (Kiel, Germany).