In recent years, flathead grey mullets (Mugil cephalus) cultured in Eilat (Israel) have been highly affected byVibrio harveyi, showing neurological signs such as uncoordinated circular swimming followed by high mortality rates. Despite the advances in and different approaches to control vibriosis associated withVibrio harveyi, including commercial vaccines, most of them have not succeeded in long-term protection. In this study, we evaluated the effectiveness, long-term protection, and antibody production of three vaccine preparations: heat-killed bacteria (HKB), membrane proteins denaturation (BME PROT), and internal proteins (INT PROT) developed specifically againstVibrio harveyifor grey mullets. Our results show that fish immunized with heat-killed bacteria emulsified with adjuvant presented the most effective and long-lasting protection against the bacterium, and a cross-protection against other bacteria from theharveyiclade. The effectiveness of each immunization treatment correlated with the levels of specific antibody production againstVibrio harveyiin the serum of the immunized fish.