As chairman of the Joint Chiefs of Staff, Mullen was the highest-ranking officer in the U.S. Armed Forces and diversified the top ranks of the Pentagon.

Mullen then attended the United States Naval Academy in Annapolis and was classmates with former Commandant of the Marine Corps Michael Hagee, former Chief of Naval Operations Jay L. Johnson, former Secretary of the Navy and Senator from Virginia Jim Webb, National Security Council staff member during the Iran–Contra affair Oliver North, former director of National Intelligence Dennis C. Blair, and NASA administrator Charles Bolden.

Mullen was recognized by his peers in 1987 with the Vice Admiral James Bond Stockdale Award for Inspirational Leadership skill.

[1] On 18 March 2009, Gates recommended to President Barack Obama that Mullen be re-nominated for a second term as chairman of the Joint Chiefs.

"It is my personal belief that allowing gays and lesbians to serve openly would be the right thing to do," Mullen said at a Senate Armed Services Committee hearing.

"No matter how I look at the issue...I cannot escape being troubled by the fact that we have in place a policy which forces young men and women to lie about who they are in order to defend their fellow citizens.

[17] Mullen further told the Senate that the United States needs to "bring as much pressure on [Iraq's political leaders] as [the U.S.] possibly can".

[18][19] President Obama, United States Secretary of Defense Leon Panetta and Admiral Mullen provided the certification required by the Act to Congress on 22 July 2011.

In a speech at Kansas State University,[20] Mullen outlined his views about the best application of military force in present times.

[22][23] President Obama nominated General Martin Dempsey as the next Chairman of the Joint Chiefs of Staff on Memorial Day 2011.

In December 2012, one year into his retirement, Mullen was in the news again, for having been the target of computer hacking, a situation that led to subsequent FBI investigations.

[25] On 11 July 2013, Mullen joined the board of directors of Sprint Nextel Corp directly after a buyout from SoftBank, one of Japan's largest cellular companies.

[26] In 2016, Mullen joined the Advisory Board of Afiniti, an American unicorn big data and artificial intelligence business.

[30] On 22 May 2024, Secretary of the Navy Carlos Del Toro announced that DDG 144, a Flight III Arleigh Burke-class destroyer, would be named USS Michael G. Mullen in his honor.

[41] An auditorium was dedicated in his name 1 March 2012, before a graduation ceremony at the Surface Warfare Officers School in Newport, Rhode Island.