Sergeant Major Castillo entered the Marine Corps in June 1999 and completed recruit training at MCRD San Diego, California where he graduated with 3rd Recruit training battalion, India Company. After completing Marine Combat Training and Motor Transport School, he was assigned the MOS 3533, Logistics Vehicle System Operator.
In February of 2000, Private First Class Castillo reported to 3rd Transportation Support Battalion, Okinawa. He was then transferred to Camp Kinser where he was assigned to the 31st Marine Expeditionary Unit and served as a Motor Transport Operator.
In February 2001 Lance Corporal Castillo reported to 1st Battalion 11th Marines, 1st Marine Division, where he served as an Ammo driver. In June 2001, he was meritoriously promoted to Corporal. In January 2003, Sergeant Castillo was deployed to Operation Iraqi Freedom I.
In January 2004 Sergeant Castillo was reassigned to 11th Marine Truck Platoon, where he deployed to Iraq attached to 1st Battalion 5th Marines and 3rd Battalion 1st Marines and was assigned as the Platoon Sergeant.
In December 2005 Sergeant Castillo reported to Drill Instructor School at MCRD San Diego, California. He served as a Drill Instructor, Senior Drill Instructor with Company G and H, 2nd Recruit Training Battalion.
In March 2008 Staff Sergeant Castillo reported to 1st Light Armored Reconnaissance Battalion where he served as the Platoon Sergeant and Truck Master. In September 2008, Staff Sergeant Castillo deployed to Iraq in support of Operation Iraqi Freedom 08.2. In April 2010, Staff Sergeant Castillo redeployed to Afghanistan, in the Helmand Province in Support of Operation Enduring Freedom.
In April 2011, Staff Sergeant Castillo reported to The Basic School, Quantico, Virginia where he served as the Motor Transport Operations Chief.
In May 2011, Staff Sergeant Castillo reported to Officer Candidates School, Quantico, Virginia, where he served as a Sergeant Instructor for the Officer Candidates Course.
In August 2011, Staff Sergeant Castillo reported back to The Basic School, Quantico, Virginia where he served as the Motor Transport Operations Chief.
In April 2013, Staff Sergeant Castillo was meritoriously promoted to the rank of Gunnery Sergeant and reassigned as the Company Gunnery Sergeant of Echo Company, The Basic School.
In September 2014, Gunnery Sergeant Castillo reported to Assistant Marine Officer Instructor duty at the University of California, Berkeley where he served as both the Marine Officer Instructor and Assistant Marine Officer Instructor. In December 2016, Gunnery Sergeant Castillo was selected for First Sergeant.
In June 2017, First Sergeant Castillo reported to 2d Maintenance Battalion and was assigned as the Company First Sergeant, General Support Maintenance Company.
In December 2018, First Sergeant Castillo reported to 6th Marine Regiment and was assigned as the Company First Sergeant, Headquarters Company.
In March 2019 First Sergeant Castillo was reassigned to Task Force Southwest 19.2 where he deployed to Afghanistan in support of Operation Freedom Sentinel and the Resolute Support Mission.
In March 2020 First Sergeant Castillo reported back to 6th Marine regiment and was assigned as the Company First Sergeant, Headquarters Company.
In December 2020 First Sergeant Castillo was promoted to Sergeant Major. He was assigned to First Battalion, Sixth Marines as the Battalion Sergeant Major in January 2021.
Sergeant Major Castillo's personal awards include the NATO Meritorious Service Medal, Navy and Marine Corps Commendation Medal with combat distinguishing device in Lieu of Fourth Award, Navy and Marine Corps Achievement Medal in lieu of sixth award, and the Combat Action ribbon. Sergeant Major Castillo earned a Bachelors degree in Logistics and Transportation Management in 2018.
He is married to the former Berlinda Martinez of Wilmington, California and has one son, Michael Aurelio Castillo II.