Sediment dredging activities in ports have been regularly recognised as a solution to maintain channels for transportation. However, deposited sediments and turbidity due to dredging will harm the coastal environment and ecosystems. In this study, the Mike 3 hydrodynamic models (DHI—Danish Hydraulic Institute) are applied to simulate the turbidity processes from sediment deposition activities in an offshore area near the Nghi Son port, Thanh Hoa province, Vietnam. This study firstly presents a good agreement of water level between the measured and simulated data collected in an offshore station. Further findings in turbidity dispersion plot the sediment concentration field around the disposal site. The deposition area in the North-East monsoon is distributed southward, with a value ranging from 0.01 to 0.4 kg/m3 in a radius of 2.5 km, while the northern region of Nghi Son port is affected by sediment turbidity dispersion with a value below 0.04 kg/m3 in the South-West monsoon. Last but not least, the results give a brief conclusion for the effects of depositing activities and open a new window for future research to evaluate the accuracy of sediment dispersion with measured data.