No, Kevin Spacey is not a Jew.
Spacey plays the disgraced lobbyist and Orthodox Jew, Jack Abramoff in the new film, Casino Jack. At the web site for that film you can take a "Test" to find out how corrupt you are.
Spacey has already been nominated for this role, Golden Globe Award for Best Actor – Motion Picture Musical or Comedy.
Previously Spacey played the Jewish attorney Ron Klain in the HBO film, Recount. Klain was Al Gore's chief of staff in the White House and General Counsel to Al Gore's recount committee after the 2000 election.
Spacey was born in South Orange, New Jersey, the son of Kathleen Ann, a secretary, and Thomas Geoffrey Fowler, a technical writer and data consultant. According to rumor, Spacey's father was an antiSemite.