Microplastics (MPs) have emerged as one of the major environmental pollutants currently. MPs (<5mm) being very tiny toxic particles coming from various anthropogenic sources impact both terrestrial and aquatic plant species by upsetting the physiological, anatomical, morphological, and genetic processes of plants. MPs in aquatic ecosystems have been reported to cause toxicity in aquatic plants and enter the food chain. Similarly, several terrestrial plants especially agricultural plant species have also been affected by MPs which may ultimately affect humans. However, this MP toxicity activates plants’ defense mechanism and induces tolerance to cope with the adverse effects caused by MPs in plants. This chapter aims to highlight the reported toxicity of MPs by previous research in both terrestrial and aquatic plants, and their tolerance and defense mechanisms. Affected physiological, anatomical, morphological, and genetic aspects of plants will be discussed in this chapter which will provide new summarized research literature for future researchers to contribute more advanced conclusions.