Radiative cooling textiles (RC@Ts) and radiative warming textiles (RW@Ts) have emerged as promising alternatives for sustainable thermal management, offering passive heat dispersion without the need for energy-intensive cooling equipment or generating and retaining heat to provide thermal comfort. Recently, nanotechnology has significantly contributed to enhancing the radiative cooling capabilities of smart textiles. Recent advances and innovative ideas are reviewed in the application of nanotechnology-based approaches to develop sustainable clothing materials for radiative cooling and warming purposes. Advanced nanomaterials, novel nanofabrication processes, and groundbreaking nanoscale engineering approaches applied to smart textiles are also reported in this work. Furthermore, a comprehensive analysis is conducted to explore the cutting-edge advancements in nanotechnology and their significant impact on RC@Ts and RW@Ts, which encompasses the underlying principles, design methodologies, and potential applications, providing a detailed overview. Additionally, a strengths, weaknesses, opportunities, and threats (SWOT) analysis is performed to assess the RC@Ts and RW@Ts developed through nanotechnology. The obstacles and perspectives on future opportunities are also discussed further, envisioning the development of highly effective and adaptable cooling and warming approaches for smart textile development. Overall, this review comprehensively analyzes the transformative capabilities of nanotechnology in the context of RC@T and RW@T materials, offering a valuable overview of the latest achievements in smart and sustainable textiles and exploring future possibilities.