Abstract A novel optical sensor, based on the use of the macrocyclic receptor cucurbit[7]uril as molecular selector taking part of a sensing poly(vinyl chloride)‐based membrane immobilized onto a quartz slide surface, has been developed and tested to thiabendazole analysis. The method is built upon the increase of the thiabendazole fluorescence as a result of the supramolecular recognition event. Variables involved in the membrane construction and fluorescence measurements have been evaluated and optimized. The sensing membrane is prepared by a spin‐coating procedure (1 min at 800 r.p.m.). An increase of more than 2 fold in the fluorescence signal is observed when the supramolecular complex is immobilized into the membrane respect to that observed for the free guest. Under optimized conditions, the dispositive responds in a few seconds to thiabendazole concentrations at 10 −7 M level. In addition, the characterization of the supramolecular complex together with lifetime measurements is included.