This study employed grid-based model for estimation of nitrogen yield in the Upper Lam Phra Phloeng watershed, Thailand. Nitrogen yield portion exists in soluble form and sediment-attachment form. The algorithm used in AGNPS model is selected to simulate the nitrogen processes. The nutrient yield algorithm integrated with grid-based model was developed. Eight events were used for the model calibration with nitrogen yield data observed at two stations (M.171 and M.145). Other eights were for the model validation. The calibration was performed by adjusting nitrogen extraction coefficient. The calibration results showed that nitrogen yields in runoff and in sediment simulations were obtained with E = 0.82, R ² = 0.91 and E = 0.90, R ² = 0.93, respectively. The validation results showed that nitrogen yields in runoff simulation produced result with E = 0.63, R ² = 0.89 and nitrogen yield in sediment produced result with E = 0.70 and R ² = 0.93. This indicates that the calibrated grid-based nutrient yield model working under GIS can be applied to the nitrogen yield estimation with satisfactory accuracy.