Bis-(3-triethoxysilylpropyl) tetrasulphane (TESPT) was employed for surface modification of iron sand for use in magnetorheological elastomers (MREs). The amount of TESPT was varied at five levels (2, 4, 6, 8 and 10 wt%) relative to iron sand content to assess the optimum amount of coupling agent for interfacial bonding and damping performance. Evidence that coupling had occurred between iron sand and TESPT was identified by Raman Spectroscopy and the grafting percentage was determined by thermogravimetric analysis. Subsequently, isotropic MREs containing unmodified and modified iron sand particles and natural rubber were prepared. Crosslink density assessment by swelling testing provided evidence that the tetrasulphane group of TESPT formed crosslinks with the rubber chains. The results exhibited the advantages of TESPT as a coupling agent between iron sand particles and rubber and also revealed that 6% TESPT content produced the highest crosslink density. The effects of the amount of TESPT on dynamic mechanical properties the morphological characteristics of the MREs were also investigated.