Fiber-reinforced polymer composites (FRPCs) are very commonly used in numerous applications. However, their susceptibility to flames during service has raised a serious safety concern for human health, environment, economy, and property. Significant attention is given to the development of flame-retardant (FR) fiber composites due to their considerable role in enhancing fire and explosion safety. This review examines the fire propagation mechanism on composite materials and synergistic effects of different additives on mechanical, thermal, chemical, and structural integrity of FR FRPCs. Several methods for improving the flame retardancy of polymeric composite materials and their impact on various composite parameters are critically analyzed. The various methods of examining the flammability of fiber composites have been discussed in detail. By optimizing the type and concentration of additives, it is possible to develop next-generation FR fiber composites that offer robust performance across diverse industrial applications. Finally, a synopsis of the most recent advancements in FRPC FR technology is given, along with an overview of the opportunities and difficulties associated with sustainable flame retardancy approaches. It is expected that the insights gained from this research will provide a foundation for future innovations in FR materials, contributing to improved safety and material performance in fire-prone environments.