Exploring the effective incorporation of natural fibers into polymer composites offers a sustainable approach to finding eco-friendly alternatives that do not harm the environment. Sheep wool–based polymer composites have emerged as a promising and sustainable alternative in the field of materials science. This review comprehensively examines the recent advancements and developments in the utilization of sheep wool as reinforcement in polymer composites. The abundant availability of sheep wool as a natural and renewable resource makes it an attractive option for enhancing the properties of synthetic polymers. The unique structural characteristics of wool fibers, such as their high aspect ratio, surface morphology, and chemical composition, contribute to the improved mechanical, thermal, and flame-retardant properties of the resulting composites. This review explores the various techniques employed for preparing sheep wool fibers, including mechanical treatments, chemical modifications, and functionalization approaches, to optimize their compatibility with polymer matrices. The interfacial interactions between wool fibers and polymer matrices are also discussed, along with the effects of various processing parameters on the overall performance of the composites. The introduction of sheep wool fiber reinforcement results in a significant uptick in tensile strength, showcasing enhancements of up to 25% compared to unmodified polymers. The inherent thermal stability of sheep wool fibers leads to an enhanced thermal resistance, as demonstrated by a 15 °C elevation in the onset degradation temperature. Moreover, sheep wool fiber reinforcement precipitates a remarkable 50% reduction in peak heat release rate, thereby spotlighting augmented flame-retardant attributes. Additionally, the integration of sheep wool fibers yields a notable reduction in water absorption by up to 30%, signifying improved resistance against moisture-related degradation. Moreover, this review highlights the potential applications of sheep wool–based polymer composites in diverse fields, including construction materials, automotive components, textiles, and packaging materials. Furthermore, the environmental benefits of utilizing sheep wool as a renewable resource and its role in waste reduction from the textile industry are emphasized. However, challenges and limitations associated with sheep wool–based polymer composites are addressed, paving the way for future research directions. Overall, this review presents a comprehensive assessment of the current state of knowledge regarding sheep wool–based polymer composites, providing valuable insights for researchers, engineers, and industries interested in sustainable materials development and environmentally friendly technologies. Sheep wool is an exciting biomass which has a potential to create sustainable and innovative materials. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.