He is the son of Lieutenant General Victor H. "Brute" Krulak, who served in World War II, Korea, and Vietnam.

After his commissioning and graduation from The Basic School at Marine Corps Base Quantico, Krulak held a variety of command and staff positions.

He served in this capacity until July 12, 1991, and was assigned duty as assistant deputy chief of staff for manpower and reserve affairs (personnel Management/Personnel Procurement), Headquarters Marine Corps on August 5, 1991.

On 3 June 1969, during Operation Virginia Ridge, Company L was occupying ambush positions near the Demilitarized Zone west of Con Thien when the Marines came under a heavy volume of mortar fire and sustained several casualties.

Although seriously wounded himself, Captain Krulak unhesitatingly left his covered position and, thinking only of the welfare of his men, fearlessly maneuvered across the fire-swept terrain to ensure that his Marines were in effective defensive locations and capable of repelling an expected ground attack.

Realizing that the determined enemy soldiers had accurate range on the Marine emplacements, and unwilling to incur additional casualties, he commenced maneuvering his men to an alternate location.

After repeatedly exposing himself to the relentless fire to supervise the evacuation of the casualties, he then personally led the platoon back to the main body of his Company across 3,000 meters of rugged mountain terrain to another patrol base and, although weak from loss of blood and the pain of his injuries, steadfastly refused medical evacuation until the arrival of another officer on the following morning.

By his courage, dynamic leadership, and inspiring devotion to duty in the face of grave personal danger, Captain Krulak minimized Marine casualties and upheld the highest traditions of the Marine Corps and of the United States Naval Service.Krulak received the Golden Plate Award of the American Academy of Achievement in 1996.

The Golden Plate was presented by Awards Council member and Chairman of the Joint Chiefs of Staff, General John M. Shalikashvili, USA.

Krulak has served as the Senior Vice Chairman and Chief Executive Officer of MBNA Europe (2001–2005) and was based at the Chester campus in the UK.

Krulak also rewrote the Marine Corps' basic combat study text, MCDP 1: Warfighting, incorporating his theories on operations in the modern battlefield.