Aims: To determine the prevalence of total and pathogenic Vibrio parahaemolyticus (Vp) and V. vulnificus (Vv) in blue crabs, water and sediment from the Maryland Coastal Bays (MCBs), USA. Methods and Results: Crab, haemolymph, sediment and seawater samples were collected monthly from four sites in MCBs from February 2012 through October 2012 with environmental parameters recorded. The most-probable-number (MPN) methodology was used to enumerate Vp and Vv with presumptive colonies and the presence of virulence markers confirmed using polymerase chain reaction (PCR). Results indicate that blue crabs contained both Vp and Vv at densities (7.28 and 5.43 log MPN g(-1), respectively) higher than those reported for bivalves. In addition, markers for clinically relevant strains of both species were detected in over 30% of samples. Haemolymph, sediment and seawater samples were also routinely positive for both species and clinically relevant strains, but generally at lower densities than found in crabs (4.27, 3.28, and 2.39 log MPN g(-1) per ml(-1) Vp, and 4.28, 2.49 and 2.38 log MPN g(-1) per ml(-1) Vv). Conclusions: Blue crabs concentrate Vp and Vv at levels greater than found in water or sediment. While changes in abundance associated with temperature are apparent, there is little evidence to support differences among sampling locations. Significance and Impact of the Study: These results highlight the potential for blue crab related vibriosis and the importance of proper handling, cooking and care of this popular seafood before consumption.