The rapid growth of tourism highlights the critical need for evaluating ecological security to sustain urban ecosystems and align development with environmental priorities. This study examines the transboundary Tumen River region, focusing on the Yanbian Korean Autonomous Prefecture in China, by integrating the System Dynamics (SD) model with the Driving Force-Pressure-State-Impact-Response (DPSIR) framework. An ecological security evaluation index was developed to analyze spatiotemporal changes across five dimensions―driving force, pressure, state, impact, and response―from 2000 to 2020. The results revealed a “U-shaped” trend in ecological security, with scores declining between 2000 and 2010, followed by a significant improvement from 2010 to 2020. The observed recovery was primarily driven by reductions in the driving force and pressure indices, coupled with enhancements in the state, impact, and response indices. However, cities such as Yanji, Longjing, Tumen, and Hunchun exhibited lower ecological security scores due to factors such as meteorological variability, tourism-related pressures, declining resource quality, and reduced vegetation coverage. The findings of this study underscore the importance of cross-border cooperation among China, North Korea, and Russia to effectively manage shared ecosystems and address transboundary environmental challenges. Drawing on international governance models, this research offers actionable recommendations for achieving sustainable development in ecologically sensitive border regions.