In this study, preparation and characterization of PVDF/PMMA-co-PAMPS/silica nanocomposite membranes as a new proton exchange membrane were investigated. Polyvinylidene fluoride (PVDF) containing pendant sulfonic acid groups was synthesized by grafting through RAFT polymerization of 2-acrylamido-2-methyl-propanesulfonic acid (AMPS) from vinyl pendent groups of already modified PVDF as a macro-monomer. The synthesized PVDF graft copolymer (PVDF-g-PAMPS) was blended with miscible copolymer containing sulfonated segments (PMMA-co-PAMPS) and sulfonic acid functionalized silica nanoparticles in order to achieve high performance nanocomposite proton exchange membrane. It was found that the addition of PMMA-co-PAMPS copolymer resulted in a significant increase in porosity and slight reduction in crystallinity of the nanocomposite membranes, which favored the water uptake and proton transport at ambient temperature. Both the water uptake and the ion-exchange capacity (IEC) of the nanocomposite membranes were increased by increasing silica nanoparticles loading. The maximum proton conductivity was 20 mS/cm at 25 °C for the nanocomposite membrane containing 10% silica nanoparticles. Also, this nanocomposite membrane showed a power density as high as 34.3 mW/cm² at peak current density of 140 mA/cm². The thermal and mechanical properties of these nanocomposite membranes were also studied.