Clancy studied English Literature at Loyola College in Baltimore, graduating with the class of 1969. In a message to the usenet newsgroup alt.books.tom-clancy, he remarked that he studied English because "I wasn't smart enough to do physics." Before making his literary debut, he spent some time running an independent insurance business.

Clancy married his first wife, Wanda, in 1970. After having several children together, they divorced in 1998. Wanda was represented by Baltimore lawyer Sheila Sachs (). Divorce papers filed by Wanda in 1996 gave the reason that Tom Clancy had "committed adultery with one Katherine Huang", () supposedly a New York assistant district attorney he met on the Internet. Much of the media attention focus on the Clancys' divorce resulted from Tom's then-pending bid to buy the Minnesota Vikings.

In 1999, Clancy, at age 52, married 32-year old fellow writer Alexandra Marie Llewellyn, on June 26 (). Also, according to the Tom Clancy FAQ website:

It was previously reported in the Washington Post that he was to marry a niece of Colin Powell just after the divorce to his first wife was finalized. Clancy is known to be very protective of his personal life. He has 4 children.

In 1998, Tom Clancy attempted to purchase the Minnesota Vikings, and had a purchase agreement in place, but the deal fell through after his divorce settlement significantly decreased his net worth. He is currently the Vice Chairman of Community Projects & Public Affairs for the Baltimore Orioles.

Tom Clancy was an early, and to many, surprising defender of Islam after the 9/11 terror attacks. He was interviewed on CNN later that day. Clancy has also associated himself with General Anthony Zinni (ret.), a critic of the war in Iraq and Secretary Rumsfeld. The two have worked together on two books. Clancy has reservations concerning the war in Iraq.

 (Music)
District Six (2003)