Expanding the family of fluorescent metal clusters beyond gold, silver, and copper has always been an issue for researchers to solve. In this study, a novel type of cysteine-capped nickel nanoclusters (Cys-Ni NCs) with bright turquoise emission was developed. The as-synthesized Ni NCs showed aggregation-induced emission enhancement (AIEE) properties across Cd²⁺ and various polar organic solvents. Concurrently, solvents with different viscosities were used to explore the principle of solvent-induced AIEE of Cys-Ni NCs, revealing a positive correlation between fluorescence intensity and solution viscosity. In addition, the concentration of Cd²⁺ that induced the AIEE effect was reduced by nearly two orders of magnitude in highly viscous solvents, indicating the possibility of Cys-Ni NCs as a promising nanomaterial platform for Cd²⁺ sensing analysis. Moreover, we propose a novel fluorescent sensing method for rapid detection of Cu²⁺ based on the carboxyl group of Cys-Ni NCs coupling with Cu²⁺. Further, validation of Cu²⁺ detecting methodologies in environmental water samples with the accuracy up to 93.94% underscores their potential as robust and efficient sensing platforms. This study expands the repertoire of fluorescent metal nanoclusters for highly sensitive and selective sensing of hazardous ions and paves the way for further exploration and wide applications in Cu²⁺ detection in biological and medicine fields.