<p>We have successfully developed a novel thiourea-based chemosensorN-((6-methylbenzo[d]thiazol-2-yl)carbamothioyl)-3,5-bis(trifluoromethyl)benzamide, <b>TS</b>, specifically designed for the detection of Hg²⁺. The structure of <b>TS</b> was comprehensively characterized using techniques such as ¹H NMR, FT-IR, and fluorescence spectroscopy. <b>TS</b> exhibited exceptional fluorescence enhancement in the presence of Hg²⁺ ions when tested against a broad range of metal ions, including Cr³⁺, Co²⁺, Ca²⁺, Na⁺, Pb²⁺, Mn²⁺, K⁺, Ni²⁺, Mg²⁺, Zn²⁺, Cd²⁺, Cu²⁺, Ag⁺, and Al³⁺. The selectivity and sensitivity studies were performed in a MeOH/water (2:98, v/v) solvent system, where <b>TS</b> demonstrated a highly sensitive response to Hg²⁺ ions with a detection limit as low as 0.005&#xa0;µg/mL. Insights into the sensing mechanism were explained through fluorescence and Job's plot analysis, confirming a robust and efficient detection pathway with a 2:1 binding mode between TS and Hg²⁺. To assess its real-world applicability, recovery experiments were conducted on environmental and agricultural samples spiked with Hg²⁺ ions. The chemosensor achieved impressive recovery rates ranging from 90.0 ± 0.24% to 102.0 ± 0.58% across various concentration levels, demonstrating its accuracy and reliability. The unique attributes of <b>TS</b>, including its cost-effectiveness, simplicity, high selectivity, and ultra-sensitivity, make it an excellent candidate for the detection of trace levels of Hg²⁺ in diverse applications.</p>