The man, who cannot be named, appeared at Letterkenny Circuit Court this morning.
The man had an address in the south but is originally from the north.
The court heard that the sexual assaults happened on a male between December 1st 1993 and 31st January, 1994.
A jury was sworn in to hear the case but the man changed his plea to guilty just before the trial was due to start.
The man’s victim broke down in tears in court when the guilty plea was put before Judge John O’Hagan.
The man was remanded on continuing bail for sentencing in October.
Barrister Patricia McLaughlin also asked for a victim impact statement.