We present a layer-by-layer functionalization of gold nanorods (GNRs) by polyelectrolytes in order to control precisely the spacer surrounding the metallic nanoparticles but also to modulate its plasmonic properties. Alternate functionalization with negatively and positively charged polyelectrolytes ensures a 2 nm step control of the spacer from 0 nm up to 10 nm, depending on the number of layers. Such process changes the local refractive index and thus induces a red shift of the surface plasmon resonance. Both solution and solid samples were studied.