Mr. Creigh was 10 years old at the time.
Prosecutors said the archbishop was repeatedly told of sexual misconduct by Father Fletcher, but failed each time to turn over to the authorities “information that might be of material assistance.”
The archbishop, who was recently diagnosed with Alzheimer’s disease, testified that he had no memory of the conversation with Mr. Creigh.
Father Fletcher died in 2006, just a year after being sentenced for the rape of a 13-year-old boy in the late 1980s.
Archbishop Wilson, who vehemently denied the accusations against him and made four attempts to have the charges dismissed, faces a maximum sentence of two years.
The outcome was closely watched by survivors of sexual abuse, who said the decision should spur the church to take further action.
“This conviction in an Australian court signals that it’s time for the Vatican to show it is serious about acting on child sexual abuse, and accept Wilson’s resignation,” said Chris MacIsaac, a spokeswoman for Broken Rites, a victims’ advocacy group.