<p>This study examines the seismic performance of reinforced concrete (RC) buildings constructed with Eco-Friendly High-Performance Concrete (EHPC), with a focus on the role of masonry infill walls. Employing nonlinear static pushover analyses, eight building models with varying heights (three-story and six-story), material types (conventional RC and EHPC), and infill configurations (bare frame vs. fully infilled frame) were analyzed. The results highlight that masonry infill walls significantly enhance lateral stiffness, base shear capacity, and overall seismic resilience. Displacement and inter-story drift reductions exceeding 50% were observed in infilled models, demonstrating the critical contribution of infill walls in mitigating lateral deformations and potential damage. These effects were particularly notable in low-rise buildings, while still significant, though slightly diminished, in taller structures due to increased flexibility and higher mode effects. The use of EHPC independently offered substantial advantages, as bare EHPC frames exhibited superior performance compared to conventional RC frames, with lower displacements and drift ratios under seismic loading. The synergy of EHPC and masonry infill walls yielded the most favorable outcomes, as seen in the ME2 model (six-story EHPC infilled), which achieved the lowest displacement and drift values among all configurations. The study concludes that integrating EHPC with masonry infill walls offers a highly effective strategy for enhancing seismic performance while contributing to environmental sustainability. The findings provide valuable insights for future design practices, emphasizing the necessity of considering both advanced materials and infill wall configurations in performance-based seismic design.</p>