An HPLC method using an UV detector was developed for the simultaneous determination of nitrites, nitrates and phosphates for environmental samples. Chromatographic separation was achieved on a Phenomenex Synergi Polar-RP LC column using acetonitrile and acidified water (pH 2.7) at 60:40 v/v as mobile phase, isocratically at a flow rate of 0.800 mL/min. Baseline resolution of all the three analytes was achieved within 3 min. The calibration curves for nitrite, nitrate and phosphate in the range of 1.0 – 50.0 ppm were linear with correlation coefficients of more than 0.999 for all the analytes. The developed method was applied to water samples obtained from the wastewater treatment plant in Gaborone, Botswana. The use of HPLC technique in this study demonstrated its ability to carry out a simultaneous determination of nitrite, nitrate and phosphate in water samples. The treatment plant was found to be functioning within expectations, as it led to the removal of 97.6% nitrite, 88.0% nitrate and 90.9% phosphate from the received wastewater. Nevertheless, the concentrations of the analytes in the effluent tank were found to exceed the limits set by the Water Utilities Corporation. Results of the developed method were comparable with those of the traditional Ion chromatography method, showing accuracy values between 95.22% – 98.04%. The precision of the method for the determination of all analytes was determined by RSD values, all of which were lower than 5%. The method is of low cost, fast, has an easy procedure and avoids the use of many reagents – some of which may be hazardous.