Disclosed herein is an ethylene-propylene-diene EPDM rubber composition with improved adhesion properties. The ethylene-propylene-diene rubber composition comprises an EPDM rubber, a crystalline polyolefin, and a polyolefin containing at least one carbonyl group (--C.dbd.O) within the structure as an adhesion improver. The ethylene-propylene-diene rubber composition improves adhesion to a polar polymeric material. Specifically, the EPDM rubber composition comprises 100 phr of an EPDM rubber, 5.about.40 phr of a polyolefin containing at least one carbonyl group and 10.about.30 phr of a crystalline polyolefin resin.