A novel calix[4]arene bearing one 2,3-naphthocrown-6 and two coumarin amide units at the lower rim in partial-cone conformation was synthesized as a colorimetric and FRET-based fluorometric sensor for F(-) and Cs(+) ions. Intramolecular FRET from the naphthalene emission to the coumarin absorption affords high fluorescence selectivity toward F(-) and Cs(+) ions.