<p>The review presents an extensive analysis of emerging developments in nano-enhanced phase change materials (NEPCMs) and their growing importance in energy-efficient building uses. The study addresses how the incorporation of nanoparticles into conventional PCMs increases their thermophysical performance and thermal conductivity, accelerates phase change, and ensures higher thermal cycling stability. The article focuses on their potential for passive cooling under warm and dry climatic conditions, where low-energy and sustainable cooling systems are critical. The findings show that significant improvement in the thermal conductivity of PCMs is obtained using carbon-based nanoparticles, particularly graphite and graphene nano-platelets compared to metal and metal oxides nanoparticles. It is also shown that the integration of NEPCMs within building envelopes (walls/facades, roofs, glazing/shading, and flooring and underlay heating modules) can regulate interior temperatures, diminish peak cooling requirements, and minimize the total energy consumption. However, challenges such as nanoparticle agglomeration, interfacial thermal resistance, reduced latent heat capacity, and long-term thermo-chemical instability still impede their large-scale and durable application in building systems. Despite these limitations, NEPCMs are extremely promising for future sustainable building design. The future research must be directed toward ecologically friendly and bio-based nanomaterials, scalable production, and machine learning-predictive modeling for performance optimization. By a convergence of material innovation and intelligent building technology, NEPCMs represent an efficient pathway toward the achievement of net-zero energy targets and climate-adaptive resilient buildings suitable for harsh-climate environments.</p>