Lieutenant Colonel Frank J. Mastromauro, who calls Barnstable, MA home, graduated from Boston University in 2006 and received his commission through the Officer Candidate Course in March 2008. Lieutenant Colonel Mastromauro reported to The Basic School in March and the Field Artillery Basic Course at Fort Sill, OK, in October 2008.  Upon graduation from Fort Sill, Lieutenant Colonel Mastromauro reported to Fox Battery, 2d Battalion, 12th Marines attached to 3d Battalion, 10th Marines, Camp Lejeune, NC. During this assignment, he served as a Forward Observer with Fox Company, 2d Battalion, 2d Marines deploying to Afghanistan in 2009. Upon return, Lieutenant Colonel Mastromauro was assigned to Lima Battery as the Executive Officer and, in 2011, deployed with the 22d MEU attached to Battalion Landing Team 2/2.

In May 2012, Lieutenant Colonel Mastromauro received orders to Marine Corps Recruit Depot, Parris Island, SC. He was assigned to Second Recruit Training Battalion and served as a Series Commander with Company F and a Company Commander with Company E. Lieutenant Colonel Mastromauro was then transferred to the Recruit Training Regiment and served as the Operations Officer. Upon completing his tour in 2015, Lieutenant Colonel Mastromauro attended Expeditionary Warfare School in Quantico, VA.

In June 2016, Lieutenant Colonel Mastromauro received orders to 3d Battalion, 11th Marines in Twentynine Palms, CA, and assumed the billet of Battalion Logistics Officer. In February 2017, Lieutenant Colonel Mastromauro was assigned as the Battery Commander of Battery K and deployed supporting the Unit Deployment Program-Okinawa. Upon return from Okinawa, Lieutenant Colonel Mastromauro assumed the duties of the Assistant Operations Officer. 

In July 2018, Lieutenant Colonel Mastromauro received orders to Marine Corps Training Mission-United Arab Emirates. During this tour, he was assigned as a battalion-level advisor to the United Arab Emirates Presidential Guard. Then in July 2019, Lieutenant Colonel Mastromauro reported to Command and Staff College in Quantico, VA.

Upon completion of school in 2020, Lieutenant Colonel Mastromauro received orders back to 3d Battalion, 11th Marines. Upon arrival, he assumed the Assistant Fire Support Coordinator's duties to 7th Marines. In May 2021, Lieutenant Colonel Mastromauro assumed the responsibilities of the Battalion Operations Officer, and then in August 2021, Lieutenant Colonel Mastromauro became the Battalion Executive Officer. 

In July 2022, Lieutenant Colonel Mastromauro was assigned to 12th Marine Regiment and served as the Logistics Officer. In July 2023, he assumed the duties of the Executive Officer, 12th Marine Regiment, which was re-designated on 15 November 2023 to 12th Marine Littoral Regiment.

Lieutenant Colonel Mastromauro assumed command of 3d Battalion, 12th Marines in June 2024.