Leptospirosis is a worldwide zoonotic disease caused by a spirochaete bacterium, Leptospira. Serological detection of this micro-organism basically relies on a conventional microscopic agglutination test (MAT), which has some limitations and disadvantages. In the present study, immunoblotting has been applied as an alternative method for differentiating serogroups and serovars of leptospires. Leptospiral whole-cell lysates from a total of 26 serovars were subjected to immunoblotting using rabbit antisera against individual serovars. The findings clearly demonstrated that the pattern of immunoreactive bands could be used to differentiate between leptospires of different serogroups, consistent with MAT results. There was a multi-band pattern that was unique for the pathogenic Leptospira antigens and was not observed in the non-pathogenic Leptospira biflexa and non-leptospiral bacteria (i.e. Escherichia coli, Burkholderia pseudomallei and Helicobacter pylori). For pathogenic Leptospira species, a prominent smear-like band at approximately 19-30 kDa was present when the antigens were probed with the homologous antisera. The molecular size of the prominent band, although it showed a cross-reaction between members within the same serogroup, differed among different serovars. The results obtained from polyclonal antibodies (antisera) were confirmed using mAb. With its simplicity and safety of experimental procedures, it is proposed that immunoblotting may potentially be useful as an alternative method for differentiating between serogroups of leptospires.