Renowned Corriedale breeder Bill Bain, of Roxburgh, said receiving such a score was "unusual and exceptional".
Mr Bain said the technique to creating a good fleece was simple. "You've got to breed good sheep and got to keep them well fed during the year."
Mr Paterson sheared the sheep in August.
Between August and February, he stored the fleece away and took it out a week ago to make sure it "looked nice".
A fleece is judged on its weight, colour, soundness, length, crimp, formation, brightness and freedom from fault.
Mr Paterson and his team will now decide whether to compete in June's national Golden Fleece competition in Wanaka.
Central Otago farmer Andrew Paterson, who has entered in similar competitions before, said a perfect 100 out of 100 score was rare in New Zealand, although it had been achieved before — he scored 100 about six years ago.
"It's not very common but [Greg Paterson's] must have been an exceptional fleece to be that good."
The Mt Benger A&P Show was held at the Roxburgh Racecourse last Friday and Saturday.
This was the third year at the racecourse.
The A&P show had picked up from low numbers a few years ago, president Dick Michelle said.
"A mix of diverse people on the committee moved away from the traditional A&P format, including events in conjunction with the show."
Last year the show featured the Otago-Southland regional final of the FMG Young Farmer of the Year and in 2016 hosted the Goldfields Cavalcade.
This year, committee member and show MC Mark Reid said they did not need another event of such prominence.
"Because we've grown so much we don't need a third act."
