With the unique advantages of cost-effectiveness and low energy consumption, constructed wetlands (CWs) are commonly used for treatment of secondary municipal wastewaters. Over the last decades, CWs have gained increased popularity for treating agricultural runoff and agro-industrial wastewater. This review highlights the practice, application, and research on wetland technology, placing them in the overall context of the need for reliable and sustainable solutions to managing agricultural runoff and agro-industrial wastewater. A critical assessment of the performance and effectiveness of wetland systems for removing various contaminants of importance to agriculture is presented. The design parameters and operational conditions affecting the efficiency of contaminant removal in CWs receiving agricultural runoff and agro-industrial wastewater are also discussed. The role of proper pretreatment, artificial aeration, effluent recirculation, in-series design, and microbial dynamics on the enhancement of treatment is provided. Challenges and perspectives for future research on agricultural treatment wetlands are also addressed.