Abstract: Water and sediment samples were collected from Uppanar estuary (harbor) and analyzed the distribution of THB and pathogenic bacteria. Totally 10 strains were isolated from those samples and three strains were selected based on the growth which were identified up to species level, Viz, Vibrio cholerae and Vibrio parahaemolyticus and Escherichia coli. In the present study the population density of pathogenic bacteria were recorded as maximum values of E. coli (5.9x104 cuf mL-1, 4.7x104 cfu g-1), V. cholerae (6.3x104 cfu mL-1, 5.7x104 cfu g-1) and V. parahaemolyticus (6.2x104 cfu mL-1, 7.3x104 cfu g-1). After tsunami there is no detailed work in this aspect (Cuddalore fishing harbor). Having with this in mind the present study was carried out to detect the bacterial densities.