Abstract A little knowledge still available for fish digenean, although some of them have pathogenic and economic importance. Fish morbidity and mortalities were reported in two fish farms culturing D. labrax fingerling with the primarily isolated parasites belonged to fish digenean trematodes. Therefore, this study was directed mainly to investigate the main causative digenean parasites. Additionally, the ecological water parameters were reported, and the anthelmintic efficacy using levamisole was evaluated. The prevalent digenean parasite was identified Digenean, Transversotrema haasi, an extra-intestinal digenean that was mainly isolated from gill and skin. The infected D. labrax exhibited abnormal external, and internal lesions indicative of deteriorating health status. The recorded infection rates were 48.67 and 38.67%, parasitic intensities, 6.14 and 2.4 and mortalities rates 28 and 19.33% in Manzala, and Wadi-mariot respectively. The recoded ecological parameters were ranged from 14.22 - 29.7 ^oC temperature, 7.49 - 8.36 pH, and 13.54 - 34.36 ppt for salinity. Besides, the in vitro therapeutic baths with levamisole were dose-dependent, with the highest anthelmintic efficacy at higher doses effective against digenean T. hassi. Higher anthelmintic efficacy was obtained at 70 µg/l levamisole concentration, the lowest mean viability 0.33, the highest parasitic mortality rate 81.81% occurred at the lowest exposure time. Although the anthelmintic efficacy of the levamisole bath has been proven, other friendly environmental agents of plant origin should be taken under consideration to avoiding potential environmental and human hazards.