<p>This review explores the interplay of thermal and magnetic properties in phase change materials (PCMs), covering both conventional (organic/inorganic) and advanced (magnetic nanocomposite) systems for energy storage and spintronics. We examine the fundamental principles of PCMs, categorizing them into organic, inorganic, and magnetic nanocomposites, while analyzing their thermal properties including latent heat, thermal conductivity, and cycling stability. The review highlights how magnetic nanoparticle integration (e.g., Fe₃O₄, Co) enhances PCM performance through magneto-thermal coupling, for achieving faster phase transitions under magnetic fields and latent heat gains in Fe-doped vanadium oxides. The key magnetic parameters—saturation magnetization (<i>M</i>_<i>s</i>), remanence (<i>M</i>_<i>r</i>), coercivity (<i>H</i>_<i>c</i>), and hysteresis—demonstrating their critical role in governing PCM functionality. The thermal-magnetic synergy enables innovative applications including: magnetocaloric-enhanced thermal energy storage (TES) systems with high exergy efficiency, spin caloritronic devices exploiting the spin Seebeck effect, and non-volatile phase-change memory with ultrafast switching. Advanced material systems such as Fe-doped <i>Ge</i>₂<i>Sb</i>₂<i>Te</i>₅ alloys and <i>LaFeSi</i> high-entropy PCMs are analyzed for their phase-dependent magnetic properties. Challenges in interfacial stability, hysteresis losses, and scalable manufacturing are discussed alongside cutting-edge solutions like 2D-material encapsulation and AI-driven material design. The review concludes with future directions emphasizing quantum-enhanced characterization, bio-inspired thermal management, and space-grade PCM development, positioning thermal-magnetic PCMs as pivotal for next-generation energy and computing technologies.</p>