Layer-by-layer assembly from aqueous solutions was used to construct multilayer thin films (<200 nm) comprising polyethylenimine and graphene oxide. Low-temperature (175 °C) thermal reduction of these films improved gas barrier properties (e.g., lower permeability than SiO x ), even under high humidity conditions, and enhanced their electrical conductivity to 1750 S/m. The flexible nature of the aforementioned thin films, along with their excellent combination of transport properties, make them ideal candidates for use in a broad range of electronics and packaging applications.