He was named bishop in 1963, and the communist regime sentenced him to house arrest. The sentence was carried out for 23 years, and Pham was not able to visit any parish in his territory until 1986.
During his period of arrest, he wrote poetic works in allegory about the life of Jesus and Christian doctrine, to help people learn it by memory.
In 1990, he was made apostolic administrator of Hanoi, and four years later became cardinal and archbishop. John Paul II kept him on the job until February of 2005, at the age of 84.
This is one of his final public appearances in December of 2005. A few months later, he became seriously ill, but continued working from his residence on behalf of the Catholic Church in Vietnam.