This study was done to detect the Leptospira bacteria in water using polyaniline (PANI) nanocomposite thin films doped with Fe-Ni using the solgel method. In this study, the electrode sensors were immersed in the Leptospira solution. The presence of pathogenic Leptospira was measured and analyzed using the current, impedance, and energy performance on current-voltage (I-V), electrochemical impedance spectroscopy, and cyclic voltammetry. The morphologies and elementary of the thin films were characterized using FESEM, TEM, AFM, EDX, and mapping. Besides that, selectivity tests were conducted to distinguish the existence of Leptospira,Pseudomonas aeruginosa, andStaphylococcus aureusbacteria. Based on the result, the presence of pathogenic Leptospira bacteria in water was successfully detected by the PANI-Fe-Ni nanocomposite thin films. The PANI-Fe-0.8-Ni(0.2)thin films have shown higher sensitivity toward pathogenic Leptospira detection. Furthermore, the FESEM and EDX analyses revealed the interaction between the microbe and thin surface by showing the irregularity of thin films of nanoparticles that range from 80 to 120 nm in size and the presence of metal in substrates. Moreover, the AFM images showed the specific morphology films' structure for Leptospira detection. Therefore, these results affirmed the potentials of polyaniline-Fe-Ni nanocomposite thin films in detecting pathogenic Leptospira for a concentration of 1 x 10(8) CFU mL(-1)in water.