Sergeant Major Giancarlo Maragni reported to Marine Corps Recruit Depot (MCRD) Parris Island, South Carolina for recruit training on 31 May 2006. Upon completing training, he reported to Camp Lejeune for Marine Combat Training and then to Lackland Air Force Base for training as a 5831 Correctional Specialist.
In October 2006, Sergeant Major Maragni reported to Camp Lejeune for duty with Brig Company, Headquarters and Support Battalion, where he performed his duties as a Correctional Specialist. In June 2008, he was meritoriously promoted to the rank of Corporal. In May 2009, Sergeant Major Maragni executed orders to Brig Section, Bravo Company, Headquarters Support Battalion in Okinawa, Japan for duties as Special Quarters Chief and Platoon Sergeant.
In December 2010, Sergeant Major Maragni reported to Drill Instructor School MCRD San Diego for duty as a Drill Instructor. Following that, he executed orders to Brig Company, Headquarters and Support Battalion, Camp Lejeune where he served as Duty Brig Supervisor and Platoon Sergeant.
In June 2013, Sergeant Major Maragni executed orders to Headquarters and Headquarters Squadron (H&HS), Iwakuni, Japan. While with H&HS, Sergeant Major Maragni was assigned as the base Marine Corps Instructor of Water Survival, Corporals Course Faculty Advisor, and Combat Marksmanship Trainer.
In June 2015, Sergeant Major Maragni reported to School of Infantry-East for duty as Combat Instructor, Combat Instructor Trainer, and Force Fitness Instructor. In January 2018, he was meritoriously promoted to Gunnery Sergeant.
In September 2018, Sergeant Major Maragni reported to Brig Company, Headquarters and Support Battalion, Camp Lejeune where he performed his duties as Company Gunnery Sergeant, Training Chief, and Company First Sergeant. In September 2020, he was assigned to 4th Law Enforcement Battalion, Headquarters Company, Detachment 2 as the Operations Chief and Senior Enlisted Advisor.
In May 2022, Sergeant Major Maragni reported to Marine Corps Air Station Cherry Point to serve as the Company First Sergeant for Combat Logistics Company 21. He then executed orders to 1st Battalion, 6th Marine Regiment in Camp Lejeune to serve as the Alpha Company First Sergeant. While with Alpha Company he deployed with the 26th Marine Expeditionary Unit (Special Operations Capable). Upon redeployment, he was moved to serve as the Weapons Company First Sergeant in March 2024.
In January 2025, Sergeant Major Maragni was transferred to Fire Support Battery, 10th Marine Regiment, where he advised and assisted in the activation of and transition to Fire Support Battalion in October 2025.
Sergeant Major Maragni was appointed as the Fire Support Battalion Sergeant Major in January 2026.