Mr. Markoff is a native of Los Angeles, California. A graduate of Los Angeles City College in 1964 with an Associate Arts degree.

He was Chairman and CEO of A-Mark Financial Corporation, a Santa Monica-based financial services company he founded in 1965 (originally named A-Mark Coin Company), that purchased the U.S. Wilkison Gold Pattern Collection and Redfield Silver Dollar hoard; the A-Mark Foundation, a private foundation he founded in 1997 became the parent of free searchable databases and other nonpartisan information covering interesting and important social issues and history, such as sites on George W. Bush, Barack Obama and Special Investigations Involving US Presidents Since 1973. In 2016, the Foundation founded the website, AboutTrump.org.

In 2004 Markoff helped found A-Mark Entertainment a company he co-chairs; and that year he also founded ProCon.org [www.ProCon.org], a 501(c)(3) public charity promoting critical thinking that as of 12-31-2019, had been, or is being used by over 10,000 schools in over 90 countries. Mr. Markoff also has an interest in Grauman's Chinese Theatre in Hollywood, acquired in 2011. In 2018, Markoff founded SexEd.net, a website giving straight forward, sourced information about sex and sexually related issues.