Stewart Burgess, now 72, was a senior house parent at Redheugh Adolescent Unit in Kilbirnie, Ayrshire, during the 1980s.
In 2008, he was found guilty of abusing two teenage boys in his care and sentenced to 10 years imprisonment.
New proceedings were raised after another former pupil came forward to report offending by Burgess at the unit, which was run by the Salvation Army for vulnerable youngsters.
During trial last month at the High Court in Paisley, prosecutors from the Crown Office and Procurator Fiscal Service (COPFS) proved that Burgess abused this victim in similar ways.
A jury heard that the victim – now in his 50s - remains traumatised by abuse, which took place between 1984 and 1985.
Redheugh is one of the institutions being investigated by the Scottish Child Abuse Inquiry, chaired by Lady Smith. The unit closed in 1994.
At the High Court in Glasgow today (21 April), Burgess, from Cumnock in Ayrshire, was sentenced to three and a half years imprisonment.
His name was added to the sex offenders register indefinitely.
Scotland’s Procurator Fiscal for High Court Sexual Offending, Fraser Gibson, said:
“Stewart Burgess selfishly and callously abused young boys in his care. The victim in this case bravely came forward to report what happened to him as a child.
“His evidence of crimes which had not been dealt with previously allowed us to prosecute this offender again. I sincerely hope the victim finds some small comfort in holding Burgess accountable for his actions.
“COPFS prosecutors are committed to pursue justice for victims of child sexual abuse, no matter how long ago the offences occurred.
“I urge any victims of similar crime to have confidence that time is no barrier. Please come forward, report it and seek support.”