<p>The accumulation of waste glass in landfills constitutes significant environmental problems due to its substantial volume, slow decomposition rate, and the challenges associated with recycling. In this study, waste glass powder (WGP) and nano-silica (NS) were proposed as cementitious replacements to mitigate alkali-silica reaction (ASR). Various compositions were used in mortar productions: 10%, 15%, 20%, and 25% WGP, combined with 1%, 1.5%, and 2% NS as cementitious replacement. NS was utilized to accelerate early-age hydration reactions in mortar, while WGP was used to mitigate ASR. An accelerated mortar bar test was conducted, and measurements of compressive and flexural strengths and capillary water absorptions were taken. Additionally, scanning electron microscopy, X-ray diffraction, and thermo-gravimetric analysis results were presented for selected mixes to investigate the impact of WGP and NS on mechanical properties, durability, microstructure, and pozzolanic reaction of mortars. The results showed that WGP and NS effectively reduced the expansion of mortars without causing significant alterations to other properties. These findings may enhance the durability and performance of cement-based materials and significantly contribute to sustainability by reducing the carbon footprint associated with cement production.</p>