<p>The construction industry is undergoing a paradigm shift toward sustainable, high-performance materials that balance durability and multifunctionality. Nano-engineered cement composites (NECC) have emerged as a transformative solution, integrating nanomaterials into traditional cement matrices to address critical limitations of conventional cement-based materials. This review synthesizes recent advancements in NECC, highlighting their impact on mechanical and functional properties. The incorporation of nanoparticles (nano-silica, nano-TiO₂, nano-Al₂O₃), nanocarbon derivatives (carbon nanotubes, graphene oxide), and nano clays enhances microstructural densification, crack resistance, and mechanical strength. Additionally, NECC exhibit superior durability, resisting sulfate and chloride attacks, carbonation, acid exposure, and freeze-thaw cycles. Sustainability remains central to NECC development, with clinker reduction and nano based alternatives to ordinary Portland cement (OPC) significantly lowering CO₂ emissions and energy consumption. The use of recycled and waste-derived nanomaterials further enhances environmental benefits, promoting low-carbon, energy-efficient binder systems. Beyond structural performance, NECC enable smart infrastructure innovations, including self-sensing composites for real-time damage detection, self-healing systems with nano-encapsulated healing agents, and photocatalytic nano-TiO₂ for pollution control and urban heat island mitigation. Additionally, thermoelectric and piezoelectric properties offer potential for energy harvesting and thermal regulation. Despite these advancements, challenges such as nanoparticle dispersion, scalability, long-term performance, and potential health and environmental impacts must be addressed. This review identifies these as critical research areas necessary to fully harness the potential of NECC in next-generation sustainable and intelligent infrastructure.</p>