This study describes a novel application of ion chromatography coupled with post-column photochemically induced fluorimetry derivatisation in alkaline medium and fluorescence detection (IC-hv-FD) for the determination of neonicotinoid pesticide, thiacloprid. In an aqueous medium, this compound showed fluorescence with an excitation maximum at 236 nm and an emission maximum at 353 nm. The 10 mmol/L NaOH with 10% (v/v) acetonitrile solution pumped at flow rate of 1.0 mL/min was used for the chromatographic elution to isocratically separate thiacloprid on an Ion Pac^®AS 11 (250 mm×4 mm i.d; 13 mm particle size, Dionex) anion-exchange column. The linear concentration range of application was 0.04-10.0 mg/L, with a relative standard deviation (RSD, n = 7) of 1.7% (for a level of 2.0 mg/L) and detection limit (LOD, S/N = 3) of 9.9 mg/L. The procedure was applied with satisfactory results to the analysis of thiacloprid in ground and lake water samples. Pesticide average spiked recoveries ranged between 95.5% and 114.0%.