AbstractIn this study, we synthesized a new thiosemicarbazone derivative molecule (5) that exhibits sensor properties. The characterization of the synthesized molecule was performed using spectroscopic methods such as 1H−, 13C–NMR, FT–IR and Q–TOF. PVC‐membrane ion‐selective sensors were prepared in which the synthesized molecule was used as an ionophore. Surface images of the prepared sensors were examined by scanning electron microscope (SEM) technique. The prepared sensors exhibited selectivity towards barium(II) ions. The developed barium(II)‐selective sensor had a low detection limit of 5.54×10−7 M in the concentration range of 1.0×10−1–1.0×10−6 M. The proposed barium(II)‐selective sensor had fast response time, good repeatability and stability, and can be manufactured with low cost. The sensor can detect barium(II) ions in various water samples with very high recoveries.