This research aimed to identify and quantify potentially pathogenic Vibrio from different cultivations of bivalve shellfi sh in the State of Santa Catarina, Brazil, and water regions in the South Bay, as well as correlate the incidence of these microorganisms with the physicochemical parameters of marine waters. Methods: Between October 2008 and March 2009, 60 oyster and seawater samples were collected from six regions of bivalve mollusk cultivation, and these samples were submitted for Vibrio counts. Results: Twenty-nine (48.3%) oyster samples were revealed to be contaminated with one or more Vibrio species. The Vibrio parahaemolyticus and Vibrio vulnifi cus counts in the samples ranged from < 0.5 log10 Most Probable Number (MPN) g-1 to 2.3 log10 MPN g-1 oyster and from < 0.5 log10 MPN g-1 to 2.1 log10 MPN g-1 oyster, respectively. Of the 60 seawater samples analyzed, 44 (73.3%) showed signs of contamination with one or more vibrio species. The counts of V. parahaemolyticus and V. vulnifi cus in the samples ranged from < 0.3 log10 MPN·100mL-1 to 1.7 log10 MPN·100mL-1 seawater and from < 0.3 log10 MPN·100mL-1 to 2.0 log10 MPN·100mL-1 seawater, respectively. A positive correlation between V. vulnifi cus counts and the seawater temperature as well as a negative correlation between the V. parahaemolyticus counts and salinity were observed. Conclusions: The results suggest the need to implement strategies to prevent vibrio diseases from being transmitted by the consumption of contaminated bivalve shellfish.