Plastic waste, especially microplastics, which has affected the receiving environment, has been increased along with the rapid development of the plastic production. Microplastics (size from 1µm to 5mm) discharged into hydrological systems can enter the human body through the food chain. This paper introduces the results of microplastic observation in some domestic wastewater samples of Hanoi city during the year 2021. The results showed that microplastic concentrations fluctuated in a high range, from 1046 to 78153 items/m3 . Fiber microplastics with their sizes less than 1000µm dominated the observed samples. The results contributed more information and dataset in the field of environmental monitoring, especially in big cities, in order to provide solutions to treat and minimize microplastic pollution. On the other hand, it is necessary to expand the survey scale to fully assess the sources of microplastic pollution in Hanoi in particular, and in Vietnam in general.