A dual-function chemosensor for Hg2+ and Zn2+ ions, inspired by the green fluorescent protein (GFP) chromophore, was designed and synthesized, which could specifically recognize Zn2+ through an “OFF–ON” fluorescence mechanism due to the restriction of the free rotation of the aryl–alkene bond, whilst also producing a selective visible colorimetric response from yellow to pink with Hg2+ ions. The response upon exposure to Zn2+ and Hg2+ is instantaneous, and the detect limits of Zn2+ and Hg2+ are 2.18×10−8 M and 4.91×10−7 M respectively.