Technical Abstract: The efficacy of a novel attenuated Edwardsiella ictaluri vaccine (B-50348) was determined in channel catfish (Ictalurus punctatus) by bath immersion and intraperitoneal (IP) injection. The vaccine was developed from a virulent strain of Edwardsiella ictaluri (AL93-58) through selection for novobiocin resistance. When channel catfish (average weight 10g) were IP injected with 4.2 × 1,000,000 colony-forming units (CFU) of the novel attenuated E. ictaluri vaccine strain, no fish died. However, when the same age and same size group of the catfish were IP injected with lesser amount (2.4 × 1,000,000 CFU/fish) of modified live RE-33 vaccine or the AL93-58 virulent strain (2.5 x 1,000,000 CFU/fish) of E. ictaluri, 65% and 95% fish died, respectively. At 15-, 30-, and 60- days post vaccination with B-50348 through bath immersion, the relative percent of survival values of vaccinated fish compared to non-vaccinated fish were all greater than 90% when channel catfish were challenged with AL93-58. At 15-, 30-, and 60- days post vaccination with B-50348 through intraperitoneal injection, when catfish were challenged with AL93-58, the relative percent of survival values of vaccinated fish compared to non-vaccinated fish were 100, 93, and 100%, respectively. Taken together, our results suggest that B-50348 could be used as a novel safe and efficacious vaccine against ESC in channel catfish.