The direct application of urban sewage treatment models to rural areas often results in increased costs and technical challenges, primarily due to a lack of considerations for local adaptability and sustainability. Constructed wetlands (CWs), as a more suitable alternative, have been increasingly recognised for their potential in addressing sewage treatment in rural areas, forming a critical water–land–energy–carbon (WLEC) nexus. Despite their promotion, systematic analyses and sustainability research on small-scale CWs in rural wastewater treatment, particularly from a WLEC nexus perspective, remain scarce. This study established a methodology framework based on a life cycle assessment (LCA) and scenario analyses to evaluate the WLEC nexus of rural CW systems and potential environmental sustainability. The methodology framework was employed in a case study of a CW system in central China. The results highlighted significant energy savings of approximately 90 % and a reduction in carbon emissions of approximately half compared with traditional wastewater treatment. While CWs provide numerous benefits, particularly in enhancing water quality, they also had notable impacts on energy and land impacts, indicating inherent trade-offs within the WLEC nexus. This study identified material optimisation as a straightforward yet highly effective strategy for mitigating environmental impacts, with water reuse emerging as a key factor for maximising benefits. These findings provided valuable insights and propose actionable solutions for the sustainable management of rural sewage, contributing to the broader discourse on the environment and resource management in rural contexts, especially in developing countries.