This dataset includes geochemical measurements made on planktic foraminifers (Morozovella velascoensis) recovered from sediment cores spanning the Paleocene-Eocene Thermal Maximum (PETM) at IODP Site 1258 (Demerara Rise, Tropical North Atlantic). Measurements include carbon and oxygen stable isotope determinations by Isotope Ratio Mass Spectrometry (IRMS, ThermoFisher, Delta V Advantage), and Mg/Ca ratios measured by Inductively-Coupled Plasma Mass Spectrometry (ICPMS, Agilent, 8900). All measurements were made between 2021 and 2023 by Chels Howard and Donald Penman at Utah State University. These measurements were made to constrain tropical Atlantic sea surface temperature and hydrologic change across the PETM.