This dataset features stable oxygen isotopes and Mg/Ca ratios of foraminifera from ODP Site 689, Maud Rise (64.5°S, 3.1°E, 2080 m water depth) spanning the late Oligocene (26.2 to 25.2 Ma). The age model was established following the magnetostratigraphic constraints of Florindo and Roberts (2005, doi:10.1130/B25541.1) and tuned to the age model of IODP Site 342-U1406 (van Peer et al., 2024, doi:10.1038/s41467-024-54186-1). The stable oxygen isotopes (d18O, in ‰ VPDB) were analysed on the benthic foraminiferal species Oridorsalis umbonatus and Cibicidoides mundulus, using a ThermoFinnigan MAT253Plus gas source mass spectrometer equipped with a Thermo Fisher Scientific Kiel IV carbonate device at Heidelberg University. The isotopic values are reported relative to the Vienna Pee Dee Belemnite (VPDB) standard, through the analysis of an in-house standard (Solnhofen limestone) calibrated to IAEA-603. Mg/Ca ratios analyses were performed on the benthic foraminiferal species Oridorsalis umbonatus, using an Agilent Inductively Coupled Plasma-Optical Emission Spectrometer 720 at Heidelberg University. The reported Mg/Ca values were normalised relative to the ECRM 752-1 standard.