This work investigates the dynamic mechanical properties of low-density polyethylene (LDPE) and natural rubber (NR) composites reinforced with coir fibre, stressing the impact of dynamic vulcanisation on stiffness, energy dissipation, and damping behaviour. Prioritising sustainability, the composites were fabricated using a two-roll mill and compression moulding, incorporating 10% and 40% fibre loadings. Dynamic Mechanical Analysis (DMA) was used to determine the storage modulus (E’), loss modulus (E’’), and damping factor (tan δ) over a temperature ranging from 30°C to 120°C and a constant frequency of 10Hz. The findings revealed that dynamic vulcanisation considerably enhanced storage modulus across all temperatures, with a 25% increase in stiffness at lower temperatures. However, as the temperature increased, the modulus decreased due to polymer chain relaxation. Coir fibre composites also had higher loss modulus values, indicating more energy dissipation, but the damping factor increased with fibre content, showing weaker fibre-matrix interactions at higher loadings. While coir fibre composites demonstrated promising mechanical and thermal properties, they were exceeded by jute, hemp, and flax fibre-reinforced composites in terms of stiffness and energy retention. These findings emphasise the potential for dynamically vulcanised coir fibre composites to be employed in applications that require improved mechanical properties and thermal stability, establishing them as a sustainable option in specific engineering contexts.