Mollusk association patterns can provide good ecological indications in coastal ecosystems. The subtidal marine environment from Gravatá to Porto Belo Island in Santa Catarina state/Brazil, was sampled from September 2001 to August 2002. Sediment was sampled in this area with a van-veen grab (0,025 m2 of sampling area) at 10 to 12 meter depths (Gravatá to Laranjeiras). At Porto Belo Island samples were taken by scuba diving with one core that sampled an area of 0,018 m2. At least five samples were collected in each station. Samples were washed in 0,5 mm mesh size sieves and fixed with 10% formalin. Similarities between samples were calculated by Jaccard coefficient. Over the similarity matrix cluster analysis were applied using the UPGMA method to form the groups. Correspondence analysis was applied to identify the mollusk association. Forty two benthic taxa were identified: 1 Polyplacophora, 7 Gastropoda and 34 Pelecypoda. Most frequent mollusks were Tellina spp., Natica livida and Abra sp. Two assemblages were identified: one encompassed the area between Gravatá to Laranjeira and the other characteristic of the Porto Belo Island.