A flow injection method (FIA) has been developed for the determination of chloride with Hg-EDTA complex as reagent. Spectrophotometric detection in the ultraviolet region at 250 nm was used for measuring the absorbance of [HgYCl]3−complex ion, where H4Y is EDTA. A manifold consisting of two lines was used. The EDTA carrier and the Hg-EDTA reagent streams were buffered at pH 4.6 (Acetate buffer). This UV-FIA method has a detection limit of 0.2 ppm chloride. At a sampling rate of 60 samples per hour, with 50 μl sample injections, high reproducibility of measurements was achieved, with about 1% relative standard deviation. The method was used for the determination of chloride in natural waters and potable water supplies. The effects of sample volume, flow rate, coil length, and possible interferences on the FIA spectrophotometric signals were reported.