Constructed wetlands (CWs) have been utilized for many years as a green technology to treat various types of wastewaters. These systems offer a land-intensive, low-energy, and low-maintenance alternative to conventional treatment methods, making them particularly suitable for small communities and remote locations. Despite their benefits, the sustainable operation and successful implementation of CWs remains a challenge. After providing a brief overview of wetlands and a summary of the current classification and use of constructed wetlands, the goal of this chapter is to provide and inspire sustainable solutions for the performance and application of constructed wetlands (CWs). To do this, it will provide a thorough review of the application and recent developments of CWs’ sustainable design, operation, and optimisation for wastewater treatment. Constructed wetlands (CWs) play a significant role in the sustainable treatment of wastewater by virtue of their operational circumstances and design characteristics, which include plant species, substrate types, water depth, hydraulic load, hydraulic retention time, and feeding mode. According to the chapter, there have been notable advancements in the design, functionality, and optimisation of CWs, which have improved the system’s sustainability and contaminated removal efficiency.