In this work, we have designed and synthesized a particular colorimetric dye sensor for the detection of heavy metal ions. Dye sensor, namely 4-hydroxy-3-(fluorophenyl-thiourea-N'-nitrilo-methylidynyl)-azobenzene was synthesized using 5-phenyldiazenyl salicylaldehyde and 4-phenylthiosemi carbazide. The dye sensor has promising properties which are applicable to detect and recognize the presence of heavy metal ions with colorimetric changing functions. Electron rich part in dye sensor structure, which can be utilized as metal binding unit, such as NH, N, S and OH (atom/group) provides the functions to coordinate metal ions. This metal ion detection property was determined by using UV-Vis absorption, (1)H-NMR peak shift and computational calculation method analysis. Furthermore, we estimated the electrochemical properties of dye sensor by using cyclicvoltammetry. In addition, the formation type of metal binding complex was determined by Job's plot measurements.