On Aug. 30, 1850, the Holy See established the Apostolic Vicariate of Phnom Penh which covered the Kingdom of Cambodia. From 1870 up to 1955, three provinces of lower Cambodia, namely: Phsardec, Chaudoc and Sroctrang (South Vietnam) were placed under the care of the Apostolic Vicar of Phnom Penh. On Sept. 20, 1955 the Holy See announced that the Apostolic Vicariate of Phnom Penh to take care of the Catholics of Cambodia alone.
On Sept. 23, 1968 the Holy See divided the Apostolic Vicariate of Phnom Penh into three ecclesiastical Circumscriptions, namely: the Apostolic Vicariate of Phnom Penh, the Apostolic Prefectures of Battambang and Kompong Cham.
The entire church was destroyed during the civil war, Khmer priests, brothers, bishop of the Apostolic Vicar of Phnom Penh were killed during the Pol Pot regime 1975-1979.
Church started again in 1990. On Jan. 18, 1990, following a request presented by a Hungarian diplomat, the government of the State of Cambodia orally agreed to the construction of a place of worship for all Christians. It would be situated about six kilometers from Phnom Penh. Its leadership would be assured by a tripartite committee made up of Catholics, various other Christian religions and the Patriotic Front.
In March 1990, the Catholics wrote to the President of the State of Cambodia to celebrate the Khmer New Year (1315th April) "according to Catholic tradition". On April 3, the Central Political Bureau of the Party gave its approval and on April 9, Mr. Chea Sim, President of the Front for National Safety, signed a letter, widely broadcasted on Cambodian radio and television, officially recognizing the existence of the Christians.
Nowadays, the Apostolic Vicariate of Phnom Penh comprises Phnom Penh City, Kep City, Sihanoukville, the provinces of Kandal, Takeo, Kampot, Kompong Speu and Koh Kong.