Bishop Vincent Long Van Nguyen​ fled Vietnam as a teenager in 1979 on a 17-metre boat jam-packed with 147 refugees.

But unlike an estimated half of the boats that sank loaded with people fleeing the new communist government in the 1970s, Bishop Long's crowded craft made it to Malaysia.

Pope Francis announced his appointment but Bishop Long's background and Parramatta status as already one of the largest Catholic dioceses in Australia and a favourite destination for new migrants, suggests the Australian Catholic Bishops Conference wish to put the issue of boat people front and centre.

"My appointment is not just about me or an individual honour, but it's an affirmation and recognition on the part of the universal church of the gifts and contributions that migrants and refugees can make to the church and also to society," Bishop Long said.

"It has a strong and and relevant message to the nation at this point in time as we tend to be a bit less welcoming to people who arrive by boat."

Born in 1961, Bishop Long entered a Catholic seminary near Saigon three years before the South Vietnamese capital fell to the North Vietnamese.

In 1975 the new rulers started closing religious training colleges and Bishop Long, expecting to drafted to fight in Vietnam wars against China and the Khmer Rouge, followed two older brothers and fled overseas.

He taught himself English during his 16 months in the Malaysian camp and in 1980 arrived as a 19-year-old in the Melbourne suburb of Springvale.

"Coming to Australia by boat as a refugee from Vietnam, I found myself a newcomer in Melbourne. I now consider myself a newcomer to the diocese of Parramatta," Bishop Long said.

"I know I'll be enriched by the many cultures that make up Western Sydney and the Blue Mountains."

As a new chum in Springvale he was so impressed by the work of the Franciscan friars that two years after arriving in Australia, Bishop Long became a Conventual Franciscan, an order popularly known as greyfriars.

He was ordained in 1989 and after a period in Rome returned to Australia to serve as parish priest at Our Lady of the Rosary, Kellyville, NSW, for four years before returning to Melbourne to take up a similar appointment at Springvale for seven years.

He was elected superior of the Order of Friars Minor Conventuals in Australia in 2005 and three years later transferred to Rome appointed assistant general, responsible for the order's Asia-Oceania section.

In May 2011 Pope Benedict XVI appointed him an auxiliary bishop of Melbourne, Australia's first Asian Catholic bishop. Subsequently, he met met Pope Francis, first as a cardinal and then when the returned to Argentina as pontiff.

The resident of the Australian Catholic Bishops Conference, Archbishop Denis Hart, welcomed Bishop Long's new appointment to Parramatta.

"After distinguished leadership in the Conventual Franciscans, Bishop Vincent Long van Nguyen has been auxiliary bishop in Melbourne since 2011, working as a gifted and compassionate pastor, Episcopal Vicar and chair of the Victorian Catholic Education Commission."

He said the bishop's "Christ-like gifts and simplicity will serve the people of his new diocese so well".

He is the fourth man to be appointed bishop to one of the Catholic Church's fastest growing dioceses in migrant-rich western Sydney. About 30 per cent of the population identify as Catholic.

Parramatta has been vacant since September 2014 after Archbishop Anthony Fisher was elevated to Archbishop of Sydney, replacing Cardinal George Pell.