McCarthy was educated at Columbia University and New York Law School, and has served as a professor at the latter and at Fordham University Law School.

He is currently a senior fellow at the Foundation for Defense of Democracies, serving as the director of the FDD's Center for Law and Counterterrorism. He has served as an attorney for Rudy Giuliani, and is also a conservative opinion columnist who writes for National Review and Commentary.

He has defended the practice of waterboarding as not necessarily being torture, and as necessary in some situations to prosecute the War on Terror whilst admitting that "waterboarding is close enough to torture that reasonable minds can differ on whether it is torture".

During the 2008 Presidential election campaign, Andrew McCarthy wrote a number of posts on the National Review's Corner blog stating that he thought that Democratic Presidential candidate, Barack Obama, was not serious about protecting U.S. national security against threats from radical Islam and elsewhere, and that Obama had a number of troubling ties and associations with leftist radicals.

In an opinion posted on the blog 'the Corner' on 10/22/08 , Mr. McCarthy wrote "I believe that the issue of Obama's personal radicalism, including his collaboration with radical, America-hating Leftists, should have been disqualifying."

In May 2009, Mr. McCarthy provided details of a letter declining an invitation from Attorney General Eric Holder for a round-table meeting with President Barack Obama concerning the status of people detained in the War on Terror. Mr. McCarthy noted his dissension with the administration in their policies regarding the detainees. On December 5, 2009 he came out publicly against prosecuting Islamic terrorists in civil courts rather than military tribunals, saying "A war is a war. A war is not a crime, and you don’t bring your enemies to a courthouse."

McCarthy has long been a die-hard fan of the New York Mets.