In this work, a widely used pesticide named carbaryl, present in numerous water supplies, has been determined by the so-called heavy atom induced room-temperature phosphorescence (HAI-RTP) methodology. A detailed study of numerous instrumental variables such as sensitivity, slits, decay time, and gate time, and those of experimental type such as heavy atoms, oxygen scavenger, temperature, buffer solutions, and organic solvents, have been carried out. The detection limit was 2.8 ng mL(-)(1) with a relative standard deviation of 2.12% at the 150 ng mL(-)(1) level. Spiked irrigation water samples taken from different places near agricultural fields gave mean percentage recoveries of 95.7%. The results obtained in this study indicate that the proposed method is suitable for the determination of residues of carbaryl pesticide in water samples with good reproducibility and sensitivity for the analysis of this compound being rapid and very simple for routine analysis.