This dataset contains benthic foraminiferal stable carbon (δ13C) and oxygen (δ18O) isotope measurements from the Ocean Drilling Program Site 1233, located on the continental slope off southern Chile in the Southeast Pacific Ocean (41°S, 74°W; 838 m water depth). The stable isotope measurements were performed on the epifaunal species Cibicidoides wuellerstorfi and the infaunal species Globobulimina affinis, picked from the >150 µm size fraction, from the 58–74 m composite depth interval, corresponding to Antarctic Isotope Maximum 8 (~37–39.4 ka). The 2 cm sampling resolution provides sub-centennial temporal resolution (~15 years per sample) based on the age model constrained by radiocarbon dating (Lamy et al. 2004, 2007; Kaiser and Lamy, 2010) and stratigraphic alignment to the Antarctic Ice Core Chronology 2023 (Bouchet et al., 2023). Stable isotope measurements were performed on cleaned foraminiferal calcite using a Finnigan MAT 253 mass spectrometer, and values are reported relative to the Vienna Pee Dee Belemnite standard. Replicate analyses were conducted for Globobulimina affinis where material permitted, while Cibicidoides wuellerstorfi was measured once per sample. All samples were analyzed at the FARLAB (Facility for advanced isotopic research and monitoring of weather, climate and biogeochemical cycling, Department of Earth Science, University of Bergen, Norway). The dataset also includes reconstructed bottom water oxygen concentrations derived from the carbon isotope offset between the two species using an established empirical relationship (Hoogakker et al., 2025). The data were generated to document changes in intermediate water properties in the Southeast Pacific during Antarctic Isotope Maximum 8.