<p>Graphene-based nanocomposites (GBNs) are gaining increasing attention for advanced energy storage and corrosion protection due to their exceptional electrical conductivity, high surface area, mechanical robustness, and chemical inertness. While numerous reviews have discussed the general properties of GBNs, this review uniquely highlights the interdisciplinary progress at the interface of energy and corrosion applications—two domains where synergistic functionality is critical but underreported. It systematically compares recent synthesis strategies, including in situ polymerization, hydrothermal techniques, and emerging green synthesis methods, with an emphasis on how these routes affect structural control and functional performance. In energy storage, we critically evaluate the role of GBNs in enhancing supercapacitors, lithium-ion batteries, and hybrid systems by improving charge capacity, cycling life, and energy density, with special focus on graphene–polymer and graphene–TMD hybrids. For corrosion protection, this review presents a comparative insight into GBN-based coatings, discussing their superior barrier effect, electrochemical stability, and intrinsic self-healing features. Notably, it also explores the integration of GBNs with smart functionalities—such as pH-responsiveness, self-cleaning, and environmental adaptability—achieved through hybridization with metal oxides and conducting polymers. The review concludes by identifying key bottlenecks including scalability, cost-effectiveness, and long-term reliability and proposes directions involving AI-assisted material design and sustainable synthesis approaches. By bridging energy and protection technologies, this review provides a novel perspective and roadmap for future multifunctional GBN development.</p>