A comparative study of electrotransport and mechanical properties in the system (1 – x)CsH2PO4–x fluoropolymer (x = 0–0.25 mass fraction) is carried out. As the polymeric additive, ultradispersed polytetrafluoroethylene Forum, a copolymer of polyvinylidene fluoride and hexafluoropropylene, and a copolymer of tetrafluoroethylene and polyvinylidene fluoride are studied. It is shown that the fluoropolymers serve as the chemically inert and thermally stable matrix for CsH2PO4. In these polymer systems, the protonic conductivity is lower as compared with CsH2PO4 as a result of the conductor–insulator percolation effect. However, the improvement of mechanical and hydrophobic properties makes the composites more promising as compared with the pure salt CsH2PO4.