Several types of diseases occur during Asian swamp eel (Monopterus albus) culture, the most prevalent being bacterial hemorrhagic disease. In the Mekong Delta, farming Asian swamp eel (M. albus) is severely affected by a highly fatal hemorrhagic disease that causes massive economic losses. This study aimed to determine the causative agent of hemorrhagic disease in Asian swamp eels. Several clinical signs were observed, including red swollen vents, head edema, abdomen and/or internal organ hemorrhage. A total of 52 bacterial isolates were recovered on Tryptone Soya Agar from different diseased eel farms in the Mekong Delta, including Hau Giang, Can Tho, An Giang, Vinh Long, and Bac Lieu provinces. A bacterial morphology examination showed that the isolates were Gram-negative, short rod-shaped, 0.1 - 0.3 mm colony size with creamy yellow color after 24 hours incubation at 28°C. Furthermore, an assessment of the biochemical identification system indicated the presence of motile Aeromonas spp. In addition, the 16S rRNA gene sequencing results confirmed that the majority of the isolates were Aeromonas veronii. A challenge test was carried out to determine the pathogenicity of A. veronii isolates collected from the eels. The calculated LD₅₀ value of the CT07 isolate was 1.51×10⁴ CFU/eel after a 14-day injection in eels with clinical signs similar to those observed in diseased eels on the farms. Moribund eels were also sampled for histopathological examination. Moreover, antibiotic susceptibility testing of 19 isolates was performed using eight antibiotics in this study.