Sloyan started his journalistic career at the age of twenty for the Times-Union in Albany. In 1958, he switched to the Baltimore News-Post, and afterward, he joined United Press International in Washington, where he was one of the first reporters to highlight automobile safety matters raised by consumer advocate Ralph Nader. Sloyan also covered the Civil rights movement, the Cuban missile crisis, the 1963 assassination of John F. Kennedy, and the Vietnam War.