Jordan Williams from Saundersfoot has been appointed Squadron Sergeant Major of E (cadet) squadron of the Queen's Dragoon Guards.
His colleague Rachel Skinner, an A Level student at Fishguard High School, has been appointed Regimental Sergeant Major of the Dyfed Army Cadet Force.
Pembrokeshire College student Jordan Williams was the mircrophone orderly at last November's Royal British Legion Festival of Remembrance at the Royal Albert Hall and has also represented the county at shooting.
He hopes to join the Royal Military Police after completing his studies.