The design of polymeric composite materials (PCM) for the optical control of chemical substances is currently one of the actively developing fields of science “at the junction” of polymer, organic, and analytical chemistry. The purpose of this work is the preparation of PCM containing derivatives of crown ethers for the optical determination of barium ions. The polymeric composite materials containing a novel optical molecular sensor have been obtained and investigated on the basis of a number of film-forming polymers. The best results have been obtained for PCM based on polyvinyl butyral films (since the fluorescence and absorption maxima shifted by 9 and 16 nm, respectively) in the fluorescence and absorption spectra of this PCM in the presence of barium ions. This makes the proposed PCM highly promising as sensor elements for the detection of the barium ions in the aqueous solutions.