A checklist of the sponges recorded in Argentina’s shelf-break front between 37° and 45°S as well as the settlement substrates they used is provided here. A total of 45 sponge species were reported in the study area from samples obtained during stock assessment cruises of the Patagonian scallop Zygochlamys patagonica (P.P. King, 1832), with an addition of 10 species from bibliographic sources, totalling 55 Demosponge species. Considering that the region is characterized mainly by the presence of soft sandy bottoms, living molluscs or their empty shells were found to be the main substrate for the majority of the recorded species (in particular, on Fusitriton magellanicus (Röding, 1798) and Z. patagonica). Polychaete tubes represented the second most important biogenic settlement substrate for sponges in the study area. Epibiotic sponges also increase the structural complexity of the ecosystem by forming microhabitats that can be exploited as refuges for other small species, thus enhancing local biodiversity.