Here, we present carbon and oxygen stable isotope data measured on bulk carbonates samples from Site U1558. The site was drilled during the International Ocean Discovery Program engineering Expedition 390C and Expedition 393 and is part of the South Atlantic Transect (SAT), a transect drilled across the western side of the southern Mid-Atlantic Ridge at ~31°S. The data set was built analyzing samples from Site U1558 Holes A and F. The data reported here span the early Eocene-early Oligocene, according to the shipboard preliminary age model for this site, and can be used to refine the age model for this site, to correlate this site with sites from other ocean basins, and could be of help in paleoceanography-related investigations.