Abstract: To investigate the etiology of disease outbreaks during the breeding of Monopterus albus fry in Xiantao City, Hubei Province, diseased rice-field eels were sampled from the Hubei Monopterus albus Industrial Technology Research Institute Co., Ltd. Pathogen identification was conducted through bacterial isolation, sequencing, and an animal reintroduction experiment. The results revealed that Aeromonas veronii was detected in both diseased and surviving rice-field eels, accounting for 52.17% and 35.71% of the pathogenic samples, respectively. Furthermore, isolation and identification of pathogens from the primary feed, tubificid worms, also detected A. veronii, suggesting the feed as a potential source of pathogen transmission. The animal reintroduction experiment confirmed that rice-field eels infected with A. veronii developed symptoms identical to those observed in natural infections, fulfilling Koch’s postulates. This study identifies A. veronii as the primary pathogen responsible for disease in cultured Monopterus albus in the Xiantao city. These results provide a theoretical basis for the accurate diagnosis and integrated control of diseases in Monopterus albus fry in this region.