The intensifying focus on environmental issues drives the demand for materials that exert minimal stress on ecosystems. Persistence of non-degradable plastics coupled with the challenges of landfill saturation and escalating water and land pollution concerns underscores the need for alternative solutions. As plastic consumption continues to rise and waste disposal capacities face strain, the importance of biodegradable plastics and plastic waste sustainable degradation has gained substantial attention. Biodegradable polymers have emerged as a significant alternative to traditional plastics, which impose long-term environmental pollution. In contrast to conventional polymers, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is susceptible to biological degradation. Microorganisms naturally convert PHBV into elemental components, minimizing its environmental impact. In this study, we investigate the behavior of PHBV polymer compositions reinforced with two types of fibers, treated by either mercerization or N-methylmorpholine N-oxide (nmmo). Our objective is to assess the effects of accelerated weathering on the properties of PHBV and PHBV/Rapeseed (RS) microfiber biocomposites. All developed samples were subjected to accelerated weathering conditions, including water spray, UV exposure, and conditioning for up to 500 hours. Our study aims to comprehensively evaluate how exposure to accelerated weathering conditions affects the mechanical, thermal, and other properties of these biocomposites. These insights provide valuable information about their potential durability and suitability for diverse applications.