This dataset contains grain-size distribution, total organic carbon (TOC), and bulk stable carbon isotope (δ¹³C-bulk) measurements from the Holocene marine sediment core MDBT 557 and MDBT 561, collected on the southern Brazilian continental shelf. Grain-size analyses were performed using laser diffraction after removal of carbonates and organic matter. TOC and δ¹³C-bulk were determined by elemental analysis–isotope ratio mass spectrometry (EA-IRMS) following acidification to remove inorganic carbon. The data provide information on sedimentological variability and bulk organic matter composition through the Holocene and are intended to support investigations of sediment dynamics, organic carbon burial, and paleoenvironmental changes on the southwestern Atlantic shelf.