Highly sensitive diagnostic tools are crucial for individual screening during an epidemic of leptospirosis. To aid in developing a diagnostic tool for the sensitive detection of pathogenic strains, a new approach targeting nucleic acid amplification that combines quantitative PCR (qPCR) and strand displacement isothermal amplification was evaluated. The effectiveness of the combined approach, a quantitative polymerase chain displacement reaction (qPCDR), was compared with a qPCR technique. The results showed that qPCDR presented higher sensitivity (at least tenfold) and shorter reaction time than the qPCR approach for pathogenic Leptospira spp. detection. Thus, the qPCDR-based technique developed in this study is a promising approach for pathogenic Leptospira spp. detection and the further development of a diagnostic kit.