Based on the typical Suzuki coupling reaction and Schiff base reaction, a novel fluorescent molecular PCBW is synthesized and applied as a fluorescence and colorimetric sensor to detect Cu 2+ in aqueous solution. The PCBW sensor presents the aggregation-caused quenching (ACQ) effect and at 1 × 10 −5 mol L −1 it emits the strongest turquoise fluorescence in the DMSO-H 2 O system ( f w = 40%). The sensor exhibits a 'turn-off' fluorescent characteristic by adding Cu 2+ , and its fluorescent intensity shows a reliable linear relationship with the Cu 2+ concentration in the range of 0-6 × 10 −6 mol L −1 , with a detection limit of 1.19 × 10 −8 mol L −1 . Meanwhile, the PCBW sensor also exhibits the colorimetric sensing from colorless to light yellow. The sensor has good selectivity and anti-interference and its pH application range can be extended from 5 to 10. The intramolecular charge transfer (ICT) is speculated as the main fluorescence mechanism of PCBW . In addition, the sensor presents good reusability and is practicable to detect Cu 2+ in diverse aqueous samples. A novel carbazole-based PCBW molecule presents excellent fluorometric and colorimetric sensing capacity towards Cu 2+ in a DMSO-H 2 O system ( f w = 40%).