The photograph published here today shows O'Grady, a serial abuser who has served seven years in a US prison for his crimes, watching over a christening at a Rotterdam church where he used his middle name, Francis.
The expatriate community attending the Church of the Holy Heart, Christ Our Redeemer, had no knowledge of the past of the man who called himself "Brother Francis".
He also volunteered at a homeless shelter and worked at a fast-food restaurant in Rotterdam where he helped organise children's parties.
O'Grady, whose crimes include the sexual abuse of over 20 boys and girls, including a nine-month-old baby, recently returned to Ireland and is living in a hostel in Dublin city centre.
In an email to one of the Rotterdam parishioners on 30 March 2010, he referred to himself as "Brother Francis", implying that he is affiliated with a religious order.
He worked at the Rotterdam restaurant, part of a global chain, until the end of 2009 and was a regular host of birthday parties there. Prior to this he worked as a telemarketer.
O'Grady is regarded as one the world's most dangerous clerical sex abusers. He has admitted in depositions to the rape, molestation and abuse of over 20 children from 1973 onwards.
He was sent to the US after his ordination in 1971 and never served as a priest in Ireland. The 64-year-old was deported to Ireland in 2000 after serving half his 14-year sentence in prison in California for sexually abusing two brothers.
He was defrocked after his conviction and gained notoriety when he agreed to feature in a critically acclaimed documentary discussing his sexual abuse of children. In Deliver Us From Evil, released in 2006, O'Grady tells how he preyed on children and how he was moved from parish to parish by church authorities.
The documentary, which has been broadcast around the world, was aired on national television in Holland two weeks ago. Several parishioners at the Church of the Holy Heart, Christ our Redeemer, recognised him. He had been volunteering at a weekly English language religious service at the church, to facilitate expatriates.
Parishioners told the Sunday Tribune he was acting as a church deacon, helping the priest with the sacraments and organising the choir singing.
On one occasion, when the priest was late, the defrocked cleric celebrated the mass until he arrived.
Fr Avin Kunnekkadan, one of the rotating priests at the church, said he was unaware of O'Grady's criminal past.
"I did not know about his background. I did not know about his past at all," he said this weekend.
An announcement was made at the church last week informing the congregation about O'Grady's criminal past.
O'Grady also volunteered at the Missionaries of Charity in Rotterdam.
The religious order runs a homeless shelter and there is a refuge for vulnerable mothers and their children at the premises. No one at the charity was available for comment this weekend.
Last week, O'Grady was served with a civil action at his Dublin hostel by Californian attorneys Manly, McGuire & Stewart.
The firm specialises in clerical sex abuse cases and represents several of O'Grady's victims who are taking civil actions against him.
Fr Tom Doyle, a Dominican priest from Virginia in the US who has met some of O'Grady's victims, said O'Grady should never have been permitted to volunteer at the church in Rotterdam and that background checks should have been carried out.
The priest said he believed O'Grady should be institutionalised.