Here, Ti3C2Tx sheets, a representative of MXenes, with lamellar structure and hydrophilic surface are prepared, and then functionalized with sulfonated polyelectrolyte brushes (Ti3C2Tx-SO3H) through a facile surface-initiated precipitation-polymerization. The Ti3C2Tx-SO3H is then utilized as a new nanofiller to fabricate hybrid proton exchange membrane, where both acidic sulfonated poly (ether ether ketone) (SPEEK) and basic chitosan (CS) are employed as polymer matrixes. The resultant hybrid membranes are systematically characterized and measured including their microstructures, water uptake and proton conduction properties. The results demonstrate that using the sulfonated polyelectrolyte brushes, Ti3C2Tx-SO3H sheets construct efficient proton transfer pathways and connect the inherent conduction channels/paths in polymer phase. This significantly enhances the proton conduction of polymer membrane including SPEEK membrane and CS membrane, under both hydrated condition and anhydrous condition. Particularly, the incorporation of 10 wt.% Ti3C2Tx-SO3H readily offers 144% and 66% increase in proton conductivity, respectively, to SPEEK membrane and CS membrane under hydrated condition. Furthermore, the hybrid membranes achieve improved thermal and mechanical stabilities. These results herald further advances to preparing functionalized MXenes and their relevant hybrid materials with enhanced performances.