Individual nanocomposite sheets of chemically reduced graphene oxide (CRG) and poly(N-vinyl pyrrolidone) (PVP), namely CRG/PVP, have been fabricated through a simple one-pot procedure. The structure and composition of the as-prepared CRG/PVP sheets were complementarily characterized using solid-state ¹³C NMR, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and other spectroscopic measurements, demonstrating that the PVP molecules were chemically grafted on the CRG surfaces. The electrical conductivity of the individual CRG/PVP sheets was measured at different levels of relative humidity (RH) using a conductive atomic force microscopy (CAFM) system, revealing that the electrical conductivity of a CRG/PVP sheet is sensitive to RH variation with a response time of a few seconds. Given the easy mass scale production and improved electrical conductivity, we envisage that the CRG/PVP nanocomposite sheets should have a broad spectrum of applications in electrical conductivity based sensors.