Abstract Dynamic mechanical behavior of natural rubber and its composites reinforced with short coir fibers has been studied. Maxima in tan δ, E″ and the middle point of E′ vs. temperature curves of the gum natural rubber compound at different frequencies almost coincide with one another. But the maxima in tan δ and E″ do not coincide in the case of composites. It is observed that as frequency increases the values of tan δ and E″ decrease whereas the values of E′ increase in the case of both gum and the composites. The values of E″ and tan δ increase with fiber incorporation, which indicates lower heat dissipation in the gum. Two prominent peaks are observed in the tan δ vs. temperature curve of these composites due to the dynamic mechanical behavior of matrix and fiber. The additional small peak represents the dynamic mechanical behavior at the interface. The effect of chemical treatment of coir fiber on damping of composites was studied and it was found that composite with poor interfacial bonding tend to dissipate more energy than that with good interfacial bonding.