In this paper, sub-20 nm ferroelectric PVDF-TrFE copolymer nanograss structures with aspect ratios up to 8.9 were developed. This study demonstrated sub-20 nm PVDF-TrFE nanograss structures that are nanoimprinted using a silicon nanograss mold in a single step. Vertically oriented PVDF-TrFE nanopillars were poled using the developed flip-stacking poling method. According to the PFM measurements, the piezoelectricity of flat thin films fabricated in this work reaches 14.0 pm/V. The maximum output voltage of the single PVDF-TrFE nanopillar was 526 mV, and the maximum piezoelectricity of the single PVDF-TrFE nanopillar was 210.4 pm/V. The piezoelectricity of the developed PVDF-TrFE nanograss structures was 5.19 times larger than that of the PVDF-TrFE flat thin films. The developed technique is simple, economical, and easy to fabricate. The developed ferroelectric PVDF-TrFE copolymer nanograss structures, which showed enhanced piezoelectricity compared to the PVDF-TrFE flat thin films, have potential applications in nanotip-based protein biosensors, nanotip-based tactile sensors, and power nanogenerators.