The presence of microplastics (MPs), as an emerging pollutant is a growing concern in different water resources. These particles are recognized as less than 5 mm in size. Most of the studies have been carried out in surface waters and wastewater treatment plants (WWTPs), but there are few studies on MPs in drinking water treatment plants (DWTPs). This study investigates these particles in three different conventional DWTPs in the city of Tehran, Iran and aims to analyze these particles down to the size of 1 µm. A scanning electron microscope (SEM) was utilized in this study to quantitatively analyze MPs. Accordingly, the average abundance of MPs in raw and treated water samples varied from 1996±268 to 2808±80 MPs L-1 and 971±103 to 1401±86 MPs L-1, respectively. While particles smaller than 10 µm comprised 65-87% of MPs. Moreover, µ-Raman spectroscopy was used to characterize MPs. As the results, polypropylene (PP), polyethylene terephthalate (PET), and polyethylene (PE) were the most abundant identified polymers among MPs comprising more than 53% of particles. Additionally, MPs were categorized as fibers, fragments and spheres. This study fills the knowledge gap of MPs presence in Tehran DWTPs which is of high importance since they supply drinking water for more than 8 million people and investigates the performance of conventional DWTPs in removing MPs.