A rubber composition includes (i) an .alpha.,.beta.-unsaturated nitrile conjugated diene rubber containing structural units derived from a conjugated diene in an amount of 30 to 60 mass % with respect to the total structural units, (ii) an ethylene-.alpha.-olefin-nonconjugated diene copolymer rubber having a limiting viscosity of 3.3 dl/g or more measured at 135.degree. C. in a decalin solvent, and (iii) a crosslinking agent. The rubber composition can produce a crosslinked rubber and a molded article exhibiting excellent oil resistance and heat resistance in a well-balanced manner.