The purpose of this study is to investigate the effect of surface modification of volcanic ash particles on dynamic mechanical properties of volcanic ash filled polyphenylene sulfide (PPS) composites. For this purpose volcanic ash particles were modified with 1, 3, 5 vol.% of 3-aminopropyltriethoxysilane (3-APTS) which has an organic functional group. All volcanic ash/PPS composite samples were prepared by using DSM Xplore 15 ml twin screw microcompounder and DSM Xplore 12 ml injection molding machines. The content of volcanic ash in composite samples was varied as 10 and 15 wt%. Volcanic ash filler dispersion and adhesion between volcanic ash particles and PPS matrix were examined by scanning electron microscopy. Dynamic mechanical properties such as storage modulus (E') and glass transition temperature (T-g) were investigated by TA Instruments Q800 dynamic mechanical analyzer. During the experiments, the relation between silane coupling and dynamic mechanical properties was evaluated.