In this study, synthetic graphite, carbon fiber, and carbon nanotube were used as thermal conductive fillers and ethylene-propylene-diene (EPDM) as matrix. Oriented EPDM/filler composites were prepared with two-roll mill, and the effects of orientation and content of carbon based fillers on thermal conductivity and tensile strength of the composites were investigated. Parallel thermal conductivity of the oriented composites is significantly higher than normal thermal conductivity of the oriented composites. Especially, at 31.6% graphite content, parallel thermal conductivity of oriented composites is 7.14 W/mK. Very high thermal conductivity was achieved for oriented EPDM/graphite composites. Orientation of the fillers using two-roll mill significantly improves the thermal conductivity in the orientation direction. For all the EPDM/filler composites, tensile strength of orientation direction is higher than that of normal direction. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41000.