Polymers and their composites have played an important role in industrial development. Polymer composites are becoming much stronger and more competitive than other materials as a result of ongoing research and development. This was made possible by newly developed techniques that could alter the physical and chemical properties of constituents. One of them is the self-reinforcement technique, which allows for the fabrication of high-strength thermoplastic polymer composites with reserved degradability, which is not possible with glass fiber/carbon fiber reinforcement. A self-reinforced polymer composite is made of a single polymeric material, which serves as both the matrix and the reinforcement. This review article discusses the use of self-reinforcement in various polymers and its impact on mechanical, thermal, and fire properties. Furthermore, the effects of process parameters (such as temperature and time, an), reinforcement structure, and mechanical property variation on the structure of self-reinforced composites are reviewed and presented in detail. In addition, the effect of foreign filler addition (such as flame retardants, inorganic particles, natural fibers, etc.) on self-reinforced composites is highlighted. In the end, the need for future research and its scope is presented.