The demand for durable and sustainable eco-friendly materials in recent times has caused many researchers to consider the use of plant fibers in composite development. In this research, the suitability of treated pawpaw fiber as a substitute for glass fiber was considered. The pawpaw fiber was extracted from the plant stem by dew retting and treated before been incorporated into the epoxy matrix. Two distinct fiber structures in linear and network forms were identified, separated, and used for the development of the composites. The composites were produced by incorporating a fixed amount of pawpaw fiber with a varied amount of glass fiber within 3–15 wt% in epoxy-based polymer matrix after which mechanical and biodegradation tests were carried out on the developed samples. Fractured surface morphology was also observed using a scanning electron microscope. The results revealed that the fiber structures influence the properties of the material. While mechanical properties were mostly enhanced by treated linear structure pawpaw fiber, biodegradation was highly promoted by treated network structure pawpaw fiber. Tensile (except for strain), hardness, and flexural properties were enhanced by the linear-structured treated pawpaw fiber, while biodegradability, impact, and tensile strain were improved by the network-structured treated pawpaw fiber compared to the control sample.