Purpose: Classical swine fever (CSF) reemerged on CSF-free Jeju Island where vaccination is not practiced by the unintentional injection of a live attenuated vaccine (modified live attenuated vaccines–low-virulence Miyagi [MLV-LOM]) in 2014. Since the Jeju provincial authority is considering adopting a voluntary immunization policy using a CSF-E2 subunit vaccine to combat LOM-derived CSF endemic, this study aimed to evaluate in Jeju herds. Materials and Methods: Two vaccination trials using the Bayovac CSF-E2 vaccine licensed for use in South Korea assessed the safety and humoral immunity of the CSF-E2 vaccine in breeding (trial 1) and nursery animals (trial 2) under farm application conditions. Results: Neither local nor systemic (including reproductive) adverse effects were objectively observed in pregnant sows and young piglets following a respective vaccination regime at pregnancy or weaning, respectively. Trial 1 showed that sows immunized with the CSF-E2 vaccine possessed high and consistent E2-specific and neutralizing antibody levels. The CSF-E2 vaccine-immunized pregnant sows subsequently conferred appropriate and steady passive immunity to their offspring. In trial 2, a double immunization scheme of the CSF-E2 vaccine in piglets at 40 and 60 days of age could elicit a consistent and long-lasting adequate antibody response. Additionally, the two trials detected no E rns -specific antibody responses, indicating that CSF-E2 vaccine can differentiate infected from vaccinated animals (DIVA). Conclusion Our trial data collectively provide invaluable information on applying the CSFE2 subunit vaccine to circumvent the possible drawbacks associated with the MLV-LOM concerning the safety, efficacy, and DIVA, in the LOM-endemic field farms and contribute to advanced CSF eradication on Jeju Island.