"To fabricate ferroelectric ultrathin polymer films with large dielectric constants for potential all-organic electronic devices, ferroelectric polymer nanotubes and a composite of the nanotubes with a dispersed organic semiconductor have been fabricated by template-assisted methods. The ferroelectricity drops markedly in spin-coated ultrathin films less than 100 nm thick, whereas P(VDF-TrFE) nanotubes with a wall thickness of a few ten nm sustain ferroelectricity. The composite nanotubes exhibit a giant dielectric constant as a result of significantly enhanced interface polarization between the nanosized fillers and the polymer matrix. They could be of practical use in supercapacitors, optoelectronic devices, and sensors.