Peter Skellern, 69, had dreamed of ordination since he was nine years old.
However after a successful career as a musician he said he never found the time.
In 2013 he was put forward for ordination training, but was diagnosed with an inoperable brain tumour.
Mr Skellern, from Lanteglos-by-Fowey in Cornwall, said: "For about a week I hung in this abyss and I just grabbed God.
"I was given a year to live and everything fell, apart from my belief in God.
"It was like that for about a week and then God closed the ground beneath me and I became resigned and happy and I have been like that ever since."
The Rt Rev Tim Thornton, Bishop of Truro, suggested he carried on with his ordination.
"It is very unusual for someone to be ordained as a deacon and a priest at the same time," Mr Skellern said.
"I was amazed Bishop Tim suggested it. It was just staggering for me. On the day I just felt wonderful."
St Wyllows Church in Lanteglos-by-Fowey saw his dream carried out, and more than 120 of his friends, family and clergy attended to watch him fulfil his 60-year-old calling.
He said: "People had come from all over, my friends from London, my friends from Cornwall and it was just wonderful."
The Bishop ordained Mr Skellern under a special faculty from the Archbishop of Canterbury, the Most Rev Justin Welby.
Bishop Tim said: "It was a privilege to ordain Peter as deacon and priest.
"It was a most unusual event and I was very pleased that the Archbishop of Canterbury was so willing to grant a faculty to allow this to happen.
He went on: "Peter has been considering a sense of vocation for a very long time and it is tragic in many ways that as he has had this calling confirmed he was diagnosed with cancer.
"It seemed right to me that he should be ordained both deacon and priest so that God can continue to work through him and, in his life and ministry, he can be faithful to becoming the person God wants him to be."
He added: "I am praying for both Peter and Diana [his wife] in this extraordinary time for them both."
