A practical hydrazine-carbothioamide-based fluorescent chemosensor TCC (N-(4-chlorophenyl)-2-(thiophene-2-carbonyl)hydrazine-1-carbothioamide) was applied for Zn²⁺ detection. TCC exhibited selective fluorescence emission for Zn²⁺ and did not show any interference with other metal ions. In particular, TCC was utilized for the detection of Zn²⁺ in paper strips, zebrafish and real water samples. TCC could detect Zn²⁺ down to 0.39 μM in the solution phase and 51.13 μM in zebrafish. The association ratio between TCC and Zn²⁺ was determined to be 2:1 by ESI-mass and Job plot. The sensing mechanism of TCC for Zn²⁺ was illustrated to be a chelation-enhanced fluorescence process through spectroscopic experiments and theoretical calculations.