Poly (2,5-benzimidazole) (ABPBI) and zirconium oxide (ZrO 2 ) nanoparticles composite membranes were synthesized. These membranes can be fabricated into tough, dense membranes by blending Poly (2,5-benzimidazole) (ABPBI) with zirconium oxide (ZrO 2 ) nanoparticles, which were characterized by using FTIR, XRD, SEM, TGA, DSC and tensile test. These composite membranes showed increased conductivity compared with original ABPBI membrane. Maximum proton conductivity at 100°C was found to be 0.069Scm −1 on 10% ZrO 2 incorporated ABPBI composite membrane, almost four times as high as the 0.018Scm −1 obtained in the case of the ABPBI membrane. The conductivity was 0.0325Scm −1 at 180°C in dry condition for ABPBI with 10% ZrO 2 nanoparticles composite membrane, higher than the conductivity 0.011Scm −1 of the ABPBI membrane at same condition. Furthermore, the composite membranes were shown to have high thermal and mechanical stability. These results suggest that ABPBI/ZrO 2 composite membranes may be a promising polymer electrolyte for fuel cells at medium or high temperature, due to their strong physical properties.