A simple spectrophotometric method for the determination of low levels of theorthophosphate (PO43-) in environmental water systems is reported. The method is based on theformation of the phosphomolybdatefrom the condensation of molybdate and orthophosphate in aqueous acid medium followed by reduction with sodium thiosulphateto form phosphomolybdenum blue. The system obeys Beer’s law at 880 nm (λmax) in the 0.005 – 0.06 mg P mL-1 phosphate concentration range. Molar absorptivity, Sandell’s sensitivity and correlation coefficient values for the determination were 57526 L mol-1 cm-1, 0.2835 µg cm-2 and 0.9948 respectively. The limit of detection was 2.213 x 10-3 mg P mL-1. The results of PO43- determination in water samples obtained using the spectrophotometric method developed in this study, compare favourably with those generated using the Murphy and Riley method which is commonly used for this analysis.Therefore, the study ably demonstrates the suitability of the present spectrophotometric method for analysis of the orthophosphate in environmental water samples.