The former archbishop of Canterbury went into the witness box at the hacking trial today to defend his friend Stuart Kuttner.
Lord Carey of Clifton said the former News of the World managing editor was a "man of integrity".
Kuttner, 74, is on trial for conspiring to hack phones at the defunct Sunday tabloid, a charge he denies.
Lord Carey said he met Kuttner after he approached media mogul Rupert Murdoch to publish a booklet entitled Jesus 2000 in the News of the World.
It was agreed that the booklet would run as a supplement in the paper.
Then after his retirement in 2002, Lord Carey said he and Kuttner worked together writing articles for the paper on moral and social issues.
Lord Carey said: "I would not normally write for a newspaper. I did for the reason there was a vast circulation and also because I thought Stuart was and is a good man. He is a man of integrity.
"I thought his integrity and concern for young journalists showed through. There was no sense of bossiness."
He added: "Mr Kuttner is a man of integrity, and man of deep loyalty to his paper, wanted to do the best for it. He is a Jew, I'm not sure how much a practising Jew.
"He is a man whose Jewish ethics went through his life and echoed mine as a deeply Christian ethic."
He said he and his wife "found a very strong friendship" with Kuttner and his wife, saying: "They did practise what they preached."