Did seattle slew and secretariat race in same race?

No, Seattle Slew and Secretariat did not race. The Triple Crown winner of 1973 (Secretariat) had already been retired for four years by the time Slew won the Triple Crown.

However, Triple Crown winners Seattle Slew and the winner of 1978, Affirmed, raced together in the Marlboro Cup. Affirmed went off as the favorite at 1-2 odds, and Slew was the second favorite, with odds of 2-1. Seattle Slew won, beating Affirmed by three lengths.

They met again in the Jockey Club Gold Cup, but Affirmed's saddle slipped, and he finished fifth. Slew ended up finishing second. Despite the defeat, many analysts considered this to be Slew's greatest performance.