We report a new sensor, 1, for sequentially detecting Zn2+ and CN- based on fluorescence. Sensor 1 was prepared through the reaction of 3-aminobenzofuran-2-carboxamide with 4-diethylaminosalicylaldehyde. Sensor 1 showed a selective "off-on" fluorescent response toward Zn2+, distinguishing Zn2+ from Cd2+. The limit of 1 (0.35 mu M) for monitoring Zn2+ is lower than the World Health Organization (WHO) guideline (76 mu M) for water available for drinking. Importantly, sensor 1 could sense Zn2+ in living cells and aqueous media. In addition, the resulting 1-Zn2+ complex functioned as an efficient "on-off" sensor for CN-. The mechanisms of 1 for detecting Zn2+ and CN- were explained by spectroscopic, spectrometric, and theoretical studies.