The adsorption of 4‐nitroanisole on silver colloidal nanoparticles was investigated by surface‐enhanced Raman spectroscopy (SERS). Actually, the chemical binding with a metal substrate may play a role in changing the electronic structure of this molecule, which can be considered a push–pull chromophore, because an internal charge‐transfer occurs between methoxy and nitrogroup. A SERS signal could be detected only in chloride‐activated silver colloids, but the spectrum recorded with green‐light excitation was not related to adsorbed 4‐nitroanisole, but to its azoderivative, formed by photoreduction of the nitrogroup on the surface of the silver substrate. Copyright © 2013 John Wiley & Sons, Ltd.