Ion exchange membranes (IEMs) play an important role in a reverse electrodialysis (RED) system for salinity gradient power generation. Challenges exist in the selection of appropriate membrane materials in order to reduce the capital cost of membrane manufacturing and in the design of proper RED membranes to optimize the energy-producing process. This work presents the synthesis of hybrid cation exchange membranes by incorporating two well-known inexpensive organic polymers with great film-forming ability. Sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) (sPPO) polymer mixed with sulfated polyvinyl alcohol (sPVA) has been proved to have great potential as a candidate for RED membranes. The prepared membranes with 2 to 10 wt% sPVA have improved the permselectivity up to 87 % and reduced area resistance down to 1.31 ohm cm-2, which is comparable to the commercially available FKS (Fumasep®, Germany) membranes. The best performance was achieved with hybrid membrane containing 5 wt% of sPVA which resulted in a gross power density at 0.46 W/m2. This power density is 14% greater than that achieved using commercial FKS membranes. This study shows a great potential of using organic-organic hybrid membranes for the RED power generation system.