Deep excavation activities commonly require groundwater dewatering to lower the water table and construct different elements in normal conditions away from the groundwater table. The dewatering process changes the groundwater properties around the dewatering well area. This change includes the water table and water flow rate and subsequently causes contamination transport. This study discusses the relationship between dewatering and contamination spread in groundwater using a numerical model. The numerical modeling was performed by the 3D finite difference technique. The effects of various parameters were explored. These parameters included well depth, contamination depth, horizontal distance between the pollution source and the dewatering well, as well as contamination source discharge and the dewatering well discharge. The effects of the aforementioned parameters on contamination spread and contamination arrival time to the dewatering well area were discussed in the results. The results indicate that increase in both well and contamination depths increased contamination arrival time to dewatering well area and decrease in contamination spread. The effect of the pumping well on the contamination spread diminished when the horizontal distance exceeds twice of the aquifer depth. Also, the increase in pumping rate decreased the arrival time; conversely, the arrival time was extended by the increase in horizontal distance.