Summary: Novel polyfunctional sulfone‐ and anhydride‐containing reactive terpolymers with different compositions have been synthesized by complex‐radical polymerization of the ternary MA‐St‐APMS acceptor‐donor‐acceptor monomer system. This method allows preparing terpolymers with a sufficiently high content of APMS which essentially increased polyelectrolyte, swelling, IEC and thermal stability of terpolymer films. The terpolymer structure‐composition‐properties (polyelectrolyte, thermal, swelling and cation exchange behavior) relationships were studied by FTIR and 1H{13C} NMR (DEPT‐135) spectroscopy, viscometry, DSC‐TGA methods, and by means of swelling and exchange capacity. The observed H‐bonding between sulfonic acid, amide and anhydride fragments played an important role in the formation of the physically crosslinked and self‐assembled architectures with controllable hydrophilic‐hydrophobic balance. These reactive terpolymers can be used as synthons for exchange membrane preparation and fuel cell applications.