Since polymer is flexible, lightweight, reliable and transparent and its material properties can easily be modified, it is a suitable substrate material for organic electronic devices, biomedical devices, and especially for flexible displays. To build a nano-device on a polymer substrate, nano to microsized patterning must be done. However, conventional photolithography cannot be used to fabricate patterns on flexible polymer substrate, due to the focusing and substrate handling issue associated with flexibility of polymer substrate and potential interaction between polymer and developer or other organic solvents used in photolithography. Degradation of polymer substrate during resist baking process over 120 °C can be another problem. In this study, 100 nm sized resist patterns were made on flexible polyethylene-terephthalate (PET) film using newly developed monomer based UV curing imprinting lithography. Compared to conventional imprint lithography, UV curing imprint lithography uses monomer based liquid phase resin and thus patterns can be fabricated without residual layer at room temperature and at much lower pressure (<3–5 atm) with UV illumination. No degradation of PET film was observed due to the imprint process and, as a result, 100 nm sized Ti–Au metal patterns were successfully formed on PET film using UV curing imprint lithography and lift-off process.