A new metal ion sensor that contains quinoline and pyridylaminophenol has been synthesized. In acetonitrile and in the presence of Zn2+, the sensor fluoresces. In contrast, in aqueous solutions the sensor fluoresces in the presence of Cd2+. The fluorescence of the molecule is selective for Zn2+ or Cd2+ and shows no fluorescence with other metal ions. The crystal structure of the Cd2+ complex shows coordination through the amide and phenol oxygens, as well as the amine nitrogen of the sensor. The sensor also acts as a colorimetric sensor for Co 2+ by changing color from colorless to yellow. The color change is selective for Co2+ and is not observed with other metal ions. The unique combination of pyridine and phenol groups with quinoline results in the properties of this sensor.