Lord Patten, the former chairman of the BBC Trust, is to take on a new role advising Pope Francis on improving the Vatican's media operations.
Lord Patten said the part-time role was "important and challenging" and would look at developing the Roman Catholic church's media outlets, including digital.
The Tory peer will chair an advisory committee over the next year which is expected to report in the summer of 2015. He said the post was unpaid.
The appointment is the latest high-profile effort by Pope Francis to shake up the Vatican since he was elected to succeed Pope Benedict last year.
The Jesuit pope has made reform of the Vatican institutions, which have been tarnished by decades of corruption and scandal, the centrepiece of his papacy.
The Vatican is expected to unveil a wide-ranging series of reforms later on Wednesday to restructure the city state's bank and its financial institutions.
Read MorePope hits out at financial speculators
Jean-Baptiste de Franssu, former head of Invesco Europe, is expected to be confirmed as new chairman of the Vatican bank, which will be radically shaken up and its powers shrunk.
"This is an important and challenging part-time assignment over the next year," Lord Pattern said. "I'm looking forward to beginning work in late September."
Lord Patten, a leading British Catholic, stepped down from the BBC Trust in the spring on health grounds and underwent heart surgery but he is easing himself back into work.
Read MoreWhat's really surprising about Hobby Lobby ruling
The Oxford university chancellor said the exact remit of his Vatican media committee would become clearer after its members met in the autumn.
Lord Patten said the committee would look especially at developing a digital strategy and ways for the church to speak to an audience beyond practising members of the faith.
Lord Patten recently waded into the heated debate about the former British colony Hong Kong and the territory's relationship with Beijing by accusing China of trying to undermine judicial independence in the global financial centre.
Read more from the FT:
Pope cuts Vatican bank down to size
tracing the travails of the Vatican bank
Vatican bank chairman to step down