Continuously polluted waters, decreasing water resources due to global warming and climate chance, and increasing labor and energy costs brought water and treatment technologies to first place on the world's agenda. Despite the continuously increasing environmental awareness and legal regulations against environmental pollution, domestic and industrial wastewaters arc discharged into the nearest receiving water bodies without any treatment. Haphazard disposal of wastes into the environment and untreated wastewater discharged into rivers and streams pollute air, water, and soil and create a danger for human, animal, and plant health. All these wastes should be treated before their disposal and discharge to leave a healthier and cleaner environment for future generations. The constructed wetlands, defined also as natural treatment systems, arc the systems emulating the natural wetland systems. They are commonly used for treatment of domestic and industrial wastewater in specially designed basins with aquatic plants and can easily be used for snull-to-medium sized communities. There are 51 constructed wetlands in the Kayseri Province of Turkey and more than three-fourths have some kind of structural failure and are not operating properly In this study, all of these constructed wetlands were investigated with regard to improper design aspects and possible failures. The common failures were identified as improper design, construction and site selection, substrate clogging and consequent (poundings), insufficient plantation, leakage through slopes, and lack of post-construction operation, monitoring, and maintenance activities. The reasons for such failures and possible corrective measures are also proposed in this study.