A fluorescent naphthalimide-tetrazine dyad (NITZ) was examined for electrofluorochromism. The reversible electrochemistry of the tetrazine was accompanied by the fluorescence change through a quasi-complete energy transfer in an electrochemical cell prepared by the mixture of polymer electrolyte and naphthalimide-tetrazine dyad. Owing to the energy transfer within the dyad (naphthalimide and tetrazine), the fluorescence efficiency of NITZ was much enhanced and the effective fluorophore concentration in this system was much less than other tetrazine based electrofluorochromic device (EFD). Thus the yellow fluorescence of NITZ was switched on and off remarkably even with small quantity of NITZ (1 wt.%) in an EFD upon application of step potentials for different redox state. Furthermore, multi-color fluorescence switching was achieved by blending a naphthalimide to the electrofluorochromic layer, to show white-blue-dark state of fluorescence. Since the tetrazine and naphthalimide units have their emission quenched at different potentials, the emission color could be tuned by quenching emission at selected wavelengths, reversibly, under low working potentials.