This dataset comprises oxygen isotope (δ¹⁸O) measurements from coral skeletons of Siderastrea stellata collected at Rocas Atoll (approximately 3.85°S, 33.81°W) in the western tropical South Atlantic. Samples of coral powder were obtained along coral cores at a sampling resolution of 0.5 mm, thereby producing a high-resolution record. The data set under consideration provides a 55-year record of δ¹⁸O, encompassing the period from 1958 to 2013.