The fisheries and aquaculture being fastest growing food sector facing the emerging threats of infestation of fish pathogens causing a huge loss. The most prevalent bacterial pathogens are Edwardsiella tarda, Aeromonas hydrophilla, Flavobacterium columnare etc. and fungus, Aphynomyces invadans. The number of fish pathogens is steadily increasing with intensification in culture practices. Conventional approach as prophylactic measures for treating the disease is through chemicals and antibiotics which resulted in in development of multiple Anti-microbial Resistance (AMR) and ecological threats, respectively. Hence, the need of the hour is to find out an alternative such as herbal medicine/ bioactive compounds from ethano-medicinal plant, to these antibiotics. Terminalia arjuna is an important ethano-medicinal plants has been used since ancient in chronic and coronary disease in floklore due to its antimicrobials, anti-inflammatory and high antioxidant potential. Despite of its huge medicinal values it has not been used in fisheries for exploring its possibility as being potent antimicrobial of fisheries significance. An in-vitro-screening was conducted to evaluate potential antimicrobial properties of arjun bark, fruit and leaf against 5 OTC resistant gram negative, 1 partial resistant, 11 OTC sensitive. Of those, 9 gram negative and 2 gram positive and 1 fungas Aphynomyces invadans was used. The study revealed that ethanolic extract of arjun bark has maximum efficacy against Edwardsiella Tarda strain (ELML-3), with a zone of inhibition 20.83±0.10 and fruit extract of arjuna showed 19.5±0.06 mm as compared to other solvent extracts as compared to standard antibiotics which showed zone of inhibition ranged from 0.0-25.17mm (OTC resistant and sensitive) with an average of 16.25±1.52mm.further, solvent extracts have their bacterial isolates specific efficacy which indicate the presence of a particular antimicrobials present in it. Antifungal activity against Aphynomyces invadans also revealed the efficacy with ethanolic extracts of arjuna leaf and bark with a zone of inhibition as 10± 0.36mm and 13± 0.53mm, respectively. Thus, present experiment suggests potentially effective solvent extracts against elite bacteria of fisheries importance such as Ethanolic bark and fruit, methanolic bark and fruit, Acetone fraction of bark ,and ethanolic extracts of bark and leaf against fungus, Aphynomyces invadans at 10 mg/ml concentration of corresponding extracts. Above mentioned solvent extracts can be utilised as broad spectrum antimicrobials after minute manipulation in dose in relation to the organism to be treated. Further, a comprehensive study is need to explore and isolate the bioactive principles for artificial synthesis of the compounds.