trans-1,3,3,3-Tetrafluoropropene (1234ze) was copolymerized under free radical conditions with vinylidene fluoride (VDF) and trifluoroethylene (TrFE), for the first time, leading to statistical poly(VDF-ter-TrFE-ter-1234ze) electroactive terpolymers. The reactivity ratios of the three comonomer couples were determined (rVDF = 0.77; rTrFE = 0.32), (rVDF = 1.67; r1234ze = 0.00), and (rTrFE = 7.56; r1234ze = 0.00), at 48 °C, using the nonlinear fitting Mayo–Lewis method. 1234ze was shown to be regularly incorporated in the terpolymer chains over the entire course of the reaction providing terpolymer chains with statistical monomer distribution and almost constant composition. These new VDF/TrFE-based terpolymers were characterized by 1H and 19F liquid state NMR spectroscopy. The characteristic NMR signals of the VDF–1234ze dyads were identified by comparing the NMR spectral signatures of a poly(VDF82-co-1234ze18) copolymer and of a terpolymer. The thermal and electroactive properties of poly(VDF-ter-TrFE-ter...