<p>The increasing global focus on environmental sustainability has accelerated the development of eco-friendly flame-retardant (FR) coatings for textiles. Conventional phosphorus/nitrogen (P/N)-based flame retardants, though highly effective in imparting fire resistance, often suffer from drawbacks such as the release of formaldehyde and limited durability, thereby raising safety and regulatory concerns. Consequently, recent research has prioritized the design of formaldehyde-free alternatives, alongside broader categories such as bio-based P/N substitutes and phosphorus-free systems. Emerging strategies involve the integration of renewable and sustainable raw materials—including biomass-derived compounds, kaolin, clays, and metal-based additives—into FR formulations. Additionally, hybrid organic–inorganic systems, advanced intumescent chemistries, and novel functional groups have been introduced to balance fire performance with ecological responsibility. The application of innovative surface-engineering techniques, such as layer-by-layer deposition, plasma-assisted modification, sol–gel processes, and nanotechnology-driven coatings, has further enhanced flame retardancy while offering multifunctionality. Nevertheless, the overall environmental performance of these systems is highly dependent on factors such as chemical composition, synthesis route, processing energy, and end-of-life behavior. Life cycle assessment (LCA) studies suggest that bio-based and polymeric FRs generally exhibit lower carbon footprints compared to traditional systems; however, their sustainability advantages are contingent upon responsible sourcing, scalability, and efficient waste management practices. This review systematically categorizes and critically evaluates recent advances in sustainable FR coatings, highlighting both their technical progress and ecological trade-offs to guide the future design of safer, high-performance, and environmentally responsible flame-retardant textiles.</p>