Microplastics as plastic pieces of ≤5 mm in size, are found in most ecosystems, both terrestrial and aquatic. Many of the microplastics find their way into the environment through the wastewater. For this reason, a knowledge of the microplastic retainment performance of wastewater treatment plants of various design is important. In this regard, several wastewater treatment processes have been studied, including new methods that are still at the development stage. This manuscript reviews the literature on such wastewater treatment methods and their ability to retain microplastics.