Citrate-capped gold nanoparticles are electrostatically assembled on amine films attached to carbon surfaces. Primary amines are covalently grafted to carbon surfaces by an electrochemically-assisted method which gives easy control of the number of amine functionalities on the surface, and hence the density of the nanoparticle assembly. Further control of nanoparticle assemblies can be gained by choice of the amine modifier, and by adjusting the nanoparticle concentration, assembly time and pH of the nanoparticle solution. This simple and versatile approach for preparation of tethered nanoparticle assemblies should be compatible with any conducting carbon substrate, giving new materials for applications ranging from catalysis to sensing.