The diocese of San Fernando, Pampanga was created on December 11, 1948, through the Apostolic Constitution Probe Noscitur; it comprised the provinces of Pampanga, Bataan, Zambales, a part of Tarlac, and Nueva Ecija. It was initially a suffragan of the Archdiocese of Manila. The first bishop was the Most Rev. Cesar Ma. Guerrero, DD, a native of Ermita, Manila, as first bishop; he received his appointment from the Vatican on May 29, 1949 and was installed on September 8 of the same year. The parish of Our Lady of the Assumption, in the provincial capital town of San Fernando, was selected as the seat of the new diocese; the parish church was thus elevated into a cathedral and was renamed Cathedral of Our Lady of the Assumption.

Taken during a major ordination rite in Floridablanca, dated 17 Dec. 1955 Bishop Guerrero established the Mater Boni Consilii (now Mother of Good Counsel) Seminary in 1950 (it was originally in Guagua, then Apalit, before being relocated to its present site in San Fernando): the Cruzada de Caridad y Penitencia (or devotion to the Virgen delos Remedios ) in 1952, which continues to this day; and Carmelite Monastery in Angeles in 1956, where he retired following his resignation on March 14, 1957 due to poor health. He died March 27, 1961 and was buried beside the monastery chapel, according to his wishes.

Eventually the diocese was dismembered when provincial boundaries became more pronounced. Zambales was established as a prelature on October 18, 1955, Nueva Ecija as a diocese on February 16, 1963, Tarlac as a diocese on May 10, 1963, and Bataan as a diocese on March 17, 1975.

The Most Rev. Emilio A. Cinense, DD, a native of Guimba, Nueva Ecija, became the second bishop of San Fernando on March 15, 1957. It was during this term that the Diocese of San Fernando was elevated into a Metropolitan See and Archdiocese; the canonical erection was held on June 15, 1975. The new archdiocese comprised the whole province of Pampanga with three suffragan dioceses, namely, the Diocese of Tarlac, the Diocese of Iba (Zambales) and the Diocese of Balanga (Bataan).

After the death of Archbishop Cinense, the Most Rev. Oscar C. Cruz, DD, the native of Balanga, Bataan and at the time rector of San Carlos Seminary, was appointed second Archbishop of San Fernando on May 22, 1978; he resigned on October 24, 19988. On January 31, 1989, the Most Rev. Paciano B. Aniceto of Sta. Ana, Pampanga former rector of the Mother of Good Counsel Seminary and Bishop of Iba, was appointed third (and first Pampanga-born) Archbishop of San Fernando; he was formally installed on March 14, 1989.

On the occasion of the Golden Jubilee anniversary of its creation as a diocese on December 11, 1998, the Archdiocese of San Fernando’s Cathedral of the Assumption was consecrated and rededicated as The Metropolitan Cathedral of San Fernando, during ceremonies presided over by the papal nuncio, the Most Rev. Antonio Franco, DD.