<p>This study investigates the influence of rice husk ash (RHA) on the properties of dynamically cured epoxidized natural rubber (ENR) and thermoplastic starch (TPS) biocomposites. To meet the demand for sustainable materials, this study uses RHA to improve the performance and degradability of bio-based composites. ENR/TPS (50/50) blends were reinforced with 10–50 parts per hundred rubber (phr) of RHA. The results revealed that the adding RHA enhanced tensile strength and modulus, with optimal reinforcement observed at 20 phr, yielding a 160% increase in tensile strength. However, excessive RHA content led to filler agglomeration, reducing mechanical performance. Thermogravimetric analysis (TGA) and temperature scanning stress relaxation (TSSR) indicated that thermal stability increased with RHA content up to 20 phr, as evidenced by a 69.1% increase in thermal resistance (<i>T</i>₉₀) and an approximately 10.0 wt% reduction in weight loss compared to the control. However, a decreasing trend was observed with further increases in RHA loading, particularly in the degradation of TPS and ENR components. Biodegradability assessments through soil burial and accelerated weathering tests demonstrated that higher RHA content led to greater weight loss, increasing from 20.0 to 65.1% at 50 phr RHA over 10&#xa0;months, confirming enhanced environmental degradation. Morphological analysis revealed a phase-separated sea-island structure, with RHA particles distributed within both the ENR and TPS phases, as well as at their interfaces. The study highlights the potential of RHA as an eco-friendly filler that enhances mechanical properties while promoting biodegradability, making ENR/TPS biocomposites suitable for sustainable material applications.</p>