Adm. Winnefeld serves as the 9th vice chairman of the Joint Chiefs of Staff and in this capacity is the nation's second highest-ranking military officer. He graduated from Georgia Tech earning a BSAE in 1978 with high honors, and received his commission through the Naval Reserve Officers Training Corps program. He subsequently served with three fighter squadrons flying the F-14 Tomcat, and as an instructor at the Navy Fighter Weapons School.

Winnefeld's unit commands at sea include Fighter Squadron 211, USS Cleveland (LPD 7), and USS Enterprise (CVN 65).  As Commander, Carrier Strike Group Two/Theodore Roosevelt Carrier Strike Group, he led Task Forces 50, 152, and 58 in support of Operation Iraqi Freedom and maritime interception operations in the Arabian Gulf.  He also served as commander, United States 6th Fleet; commander NATO Allied Joint Command, Lisbon; and commander, Striking and Support Forces NATO.

His shore tours include service in the Joint Staff Operations Directorate (J-3), as senior aide to the Chairman of the Joint Chiefs of Staff, and as executive assistant to the Vice Chief of Naval Operations.  As a flag officer, he served ashore as director, Warfare Programs and Transformational Concepts, United States Fleet Forces Command, as director of Joint Innovation and Experimentation at United States Joint Forces Command, and as the director for Strategic Plans and Policy (J-5) on the Joint Staff.  He most recently served as the commander of North American Aerospace Defense Command (NORAD) and U.S. Northern Command (USNORTHCOM).

Winnefeld's awards include the Defense Distinguished Service Medal, Distinguished Service Medal, Defense Superior Service Medal, the Legion of Merit, the Bronze Star, the Defense Meritorious Service Medal, the Meritorious Service Medal, the Air Medal, and five Battle Efficiency awards.