A total number of 100 fish samples (50 apparently healthy fish and 50 seemed to be unhealthy fish) were randomly collected from one farm of cultured Seabream fish at Domeitta provenance, Egypt. Specimens were subjected to parasitological examination for detection of isopoda infestation. The clinical signs of isopoda infested fish are erosion on gill lamella, damages on gill rakers, pale gills, hemorrhagic areas on gill cover, abdomen and on the bases of fins also abrasions and body emaciation was noticed. The detected parasites were Nerocila spp. Juvenile. The parasites detected in the gill chamber of investigated fish.  These parasites were described in details. Water samples as well as blood samples were taken for determination of water quality and changes in blood parameters due to isopoda infestation. Analysis of water samples revealed that the parasitic infestations levels have increased with decreasing level of dissolved oxygen, increasing ammonia levels, temperature, hardness, pH and salinity. Parasitic infestation resulted in remarkable decline in RBCs, hemoglobin, monocytes values together with noticeable increase lymphocytes, basophils, eosinophils and neutrophils counts. Further, trials for treatment trials of isopoda have revealed that isopoda was not affected by any concentration of all tested chemicals except the high concentration (0.150 ppm) of malathion after six days of treatment.