A Catholic brother is accused of sexually assaulting a boy he had been counselling after the youngster was molested by another man, a court has been told.

Former Vincentian brother William Stanley Irwin, 54, of Pyrmont in inner Sydney, appeared briefly in Sydney's Downing Centre Local Court today charged with two counts of gross indecency on a male under the age of 18 in the mid-1980s.

The court was told Mr Irwin was arrested last week and had since been stood down from his teaching job at St Aloysius' College at Milsons Point on Sydney's lower north shore.

Mr Irwin is the 10th man to be charged with sexually assaulting boys at a central western NSW boarding school.

His arrest follows an investigation by Strike Force Belle into claims of sexual assaults on students at two secondary colleges at Bathurst between 1960 and 1993.