A member of the Benedictine Order, Agius was appointed the Apostolic Delegate to the Philippines by Pope Pius X in 1904.

Agius attended the college operated by the monks of Abbey of Saint Augustine in Ramsgate Kent, England, where he was an outstanding student.

In 1884, the monastery was closed due to Italian-Maltese political turmoil, and Agius returned to Ramsgate to continue his religious mission.

In the Philippines, Agius canonically crowned the ivory statue of the Our Lady of the Most Holy Rosary of La Naval de Manila on 5 October 1907, representing Pope Pius.

On 15 December 1911, Agius was given a solemn Requiem Mass and was buried in the underground crypt of the Cathedral Basilica of the Immaculate Conception in Manila.

His remains were set into a smaller casket and moved to a new grave inside the Benedictine Abbey Church of Our Lady of Montserrat in Manila.

The inscription translates as: Ambrose Alfred Agius (1856 - 1911), Monk of Ramsgate, Titular Archbishop of Palmyra, Apostolic Delegate to the Islands, lies buried here; whose bones were formerly buried in the Cathedral basilica; which, destroyed by war, they were transferred to this Abbey church in the year 1945.