The halide anion effect on the adsorption of 1,2,3-triazole on Ag and An colloidal nanoparticles has been investigated by means of surface enhanced Raman scattering (SERS), UV-visible absorption spectroscopy, and scanning electron microscopy. To interpret the SERS spectra, the vibrational spectra of 1,2,3-triazole were assigned with the help of density functional theoretical (DFT) calculations of the two tautomers of 1,2,3-triazole, both free and bound to Ag and An adatoms. Upon addition of halide anions, both tautomers interact with the Ag surface through one nitrogen atom. Analogous behavior is observed in the case of basified An colloids, whereas at the usual pH of these hydrosols (similar to 6) the adsorption of 1,2,3-triazole is the same of that observed in halide-free colloids.