A novel triphenylamine-based fluorescent sensor tris((4-amino)phenylduryl)amine (m-TAPA) for Fe³⁺/Cu²⁺ ion has been developed. m-TAPA shows high selectivity and sensitivity toward Fe³⁺/Cu²⁺ over alkali and transition metal ions in aqueous solution. The possible mechanism of fluorescence quenching was that Fe³⁺/Cu²⁺ can be captured by the NH₂ groups of m-TAPA to form non-fluorescent complexes, resulting in strong quenching. The detection limits of Fe³⁺ and Cu²⁺ were calculated to be 230 nM and 620 nM, respectively. Furthermore, fluorescent test strips have been prepared for convenient detection of Fe³⁺ and Cu²⁺ ions in environmental water samples, even in drinking water.