Jennifer Grieves enlisted in the United States Marines in 1990 and served early positions as an administrative assistant and pay analyst. She subsequently completed academic study as a criminologist and military training as a pilot, securing a bachelor of arts, graduating Cum Laude, from the University of Maryland at College Park and graduating first in her class from Naval Flight Training in Pensacola, Florida. As a junior pilot, Jennifer Grieves focused on helicopter operations, serving as a helicopter squadron pilot and flight schedule writer during Operation Iraqi Freedom in Mosul, Iraq as well as stability operations in Monrovia, Liberia.

Ms. Grieves went on to serve 2 years as a deputy operations officer/pilot training manager in charge of weapons/tactics and 4 more years as an instructor pilot for the Marine Corps Presidential Helicopter Squadron serving time as an operations officer and executive helicopter program coordinator as well as commanding the Marine Corps' Presidential Helicopter. She returned to the academic environment to earn a master of arts in military studies from the Marine Corps University Command and Staff College in Quantico, Virginia. Before retiring from the Marine Corps in 2018, Jennifer Grieves directed amphibious and task force training with the Second Marine Expeditionary Force in Jacksonville, North Carolina.