Adjuvants can enhance immune response to an antigen. Viral haemorrhagic septecemia (VHS) causes heavy losses in flounder aquaculture in Korea. In this study, we evaluated protective efficacy of vaccine formulations against VHS. Formalin inactivated vaccine, prepared with or without adjuvants. Groups included, inactivated virus alone (IV), IV emulsified with squalene (IV+Sq), IV emulsified with squalene and 0.5% of aluminium hydroxide (IV+Sq+Al), IV with addition of 0.5% of aluminium hydroxide (IV+Al), IV emulsified with FIA (IV+FIA) and Sq+Al without inclusion of IV. Olive flounder (12-15 gm) were divided into 7 groups of 50 fish and 100µl of either of the above mentioned vaccine formulation was administered intra-peritonealy; control group was injected with same volume of MEM. Protection against VHSV was evaluated at 4th and 10th week post vaccination (wpv). Relative percent survival (RPS) obtained at 4th wpv was 37%, 31%, 58%, 19 %, 3% , 3% and at 10th wpv 48%, 65%, 83%, 53%, 71% and 6% respectively for IV, IV+Sq, IV+Sq+Al, IV+Al, IV+FIA and Sq+Al. Our results demonstrate that these vaccines formulated with squalene adjuvants can effectively protect olive flounder against VHSV and could offer an appropriate strategy to prevent this infection in olive flounder culture without serious side effects.