The sulphydryl-functionalized multiwalled carbon nanotubes (MWCNT-SH) are synthesized by π–π stacking interaction between 2-naphthalenethiol (NAT) and multiwalled carbon nanotubes (MWCNT). X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectroscopy confirm sulphydryl groups attach on MWCNT surface. Meanwhile, the phosphate-functionalized gold nanoparticles (AuP–NPs) are obtained by using an improved phosphorus reduction method. On the basis of the AuS bond interaction between MWCNT-SH and AuP–NPs, the all-solid-state multilayered nanostructures of MWCNT/AuP–NPs are readily formed onto an electrode surface by using the layer-by-layer (LBL) self-assembly method. Transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV/Vis), scanning electron microscopy (SEM), and cyclic voltammetry (CV) are used to characterize the film assembly process. Electrochemical investigations demonstrate that the assembled nanostructures films possess excellent electrocatalytic activity toward hydrazine oxidation as a result of the “clean” surface of AuP–NPs, and thus can be used as an electrochemical sensor for hydrazine detection with the wide linear range (6.0×10−7 to 9.0×10−3 M) and the low detection limit (2.0×10−7 M). This demonstration offers a new route to synthesis of CNTs/metal–NPs multilayered films, which is believed to be useful for the fundamental investigations of CNTs/metal–NPs nanohybrids and their possible applications.