Based on the fluoride ion recognition ability of nitro-substituted 3,3′-bis(indolyl)methane (Nbim) and unique properties of multi-walled carbon nanotubes (MWCNTs) with enlarged active surface area and high electrical conductivity, a new solid–liquid interface for the selective detection of fluoride ion in water was fabricated by a Nbim/MWCNT-modified glassy carbon electrode. To transform the molecular interactions occurring at the solid liquid interface into measurable signals, electrochemical techniques were used through the electron transfer mediator of K₃Fe(CN)₆. Because of the synergistic effect of Nbim and MWCNTs, the as-prepared electrochemical sensing interface can be applied for the selective voltammetric determination of non-electroactive analytes (F⁻) based on the changes in the peak currents of the ferricyanide/ferrocyanide couple. The response current was linear, with F⁻ concentration in the range from 1 μM to 130 μM and a detection limitation of 0.1 μM. This study offers a new strategy for the detection F⁻ by a solid interface in practical water samples.