Flexible field-emission devices (FEDs) based on reduced graphene oxide (RGO) emitters are fabricated by the thermal welding of RGO thin films onto a polymeric substrate. The RGO edges are vertically aligned relative to the substrate as a result of cohesive failure in the RGO layer after thermal welding. Even at large bending angles, excellent electron emission properties, such as low turn-on and threshold fields, a high emission current density, a high field enhancement factor, and long-term stability of the emission properties of RGO emitters, arise from the uniform distribution and high density of the extremely sharp RGO edges, as well as the high interfacial strength between the RGO emitters and the substrate. Al- and Au-doped RGO emitters are fabricated by introducing a dopant solution to the RGO emitters, and the resulting field-emission characteristics are discussed. The proposed approach is straightforward and enables the practical use of high-performance RGO flexible FEDs.