Neary was commissioned in the United States Marine Corps as a second lieutenant after graduation from Virginia Military Institute in 1988.

His staff assignments include tactics instructor, The Basic School; the Future Operations Officer of the 4th Marine Expeditionary Brigade (AT); Plans and Executive Officer for 8th Marine Regiment in support of Operation Secure Tomorrow in Haiti; Plans Observer Trainer with the Joint Warfighting Center J7 in Suffolk, Virginia; commanding officer, Marine Recruiting Station, New Jersey; and branch chief of the Programs Assessment Branch, Programs and Resources, Headquarters Marine Corps.

As a lieutenant colonel, Neary assumed command of 3rd Battalion, 8th Marines in July 2004.

Following his promotion to Colonel, Neary assumed command of 4th Marine Regiment from June 2010 to July 2012.

[2] As a major general, Neary assumed command of U.S. Marine Corps Forces Europe & Africa in July 2020.