Tetanospasmin is a neurotoxin that causes tetanus. Recently, interest has been taken in the immunogenic and adjuvant properties of the O-chain (OPS) of B. abortus shows various adjuvant activities and improved immunological responses. This study was aimed at investigating the adjuvant properties of Brucella abortus OPS, and the comparative analysis of the immunological response by the OPS-TT conjugate and the purified OPS against tetanus. OPS was extracted with a solution of 2% acetic acid and purified with a Sephadex G-50 column. Conjugate of female BALB/c mice were selected. Vaccination was performed with three doses in a two-week interval. Serum samples were collected and antibody responses against tetanus were measured by ELISA method for total IgG, IgG1, IgG2a, IgG2b, IgG3, IgM and IgA. Two weeks after the first dose, there was no significant difference between groups immunizided with TT and OPS-TT. However, following the second and the third doses, OPS-TT caused a significant increase in the concentration of all types of antibodies against tetanus, when compared to TT. The anti-TT IgG antibody was predominantly of the IgG1 subtype followed by IgG3, IgG2a and IgG2b. These results demonstrate that OPS fromB. abortus increases anti-tetanus antibody titre in a conjugate form with tetanus toxoid, and can be an appropriate and an effective adjuvant.