Industrial and domestic activities generate large volume of wastewater containing harmful inorganic and organic pollutants such as heavy metals, endocrine disruptive chemicals, antibiotics, pesticides dyes, etc., which increase biochemical oxygen demand, chemical oxygen demand. Its discharge without prior treatment causes various noxious effects on human health and aquatic and terrestrial ecosystems. Constructed wetland (CW) is considered a sustainable, effective, and eco-friendly technology for treating different types of wastewater. CWs not only effectively treat wastewater but also provide additional environmental benefits such as climate regulation, flood control, and prevention of soil erosion. They contribute to water supply, enhance aesthetic and recreational values, provide habitats for wildlife, and support plant biomass, biofuel production, and mineral cycling. However, enhancing the performance of CWs through bioaugmentation with plant growth-promoting and pollutant-degrading microbes is crucial. In this chapter, we have discussed the constructed wetlands and their wastewater treatment efficiency during laboratory and field-scale applications. Further, microbial population dynamics and their role in the elimination of different pollutants are also discussed. Additionally, the chapter highlights various factors influencing microbial population dynamics, which ultimately affect the overall performance of constructed wetlands. These insights underscore the importance of microbial ecology in optimizing CWs for effective wastewater treatment and environmental remediation.