The former Celtic gaffer spoke out after cheating former Juve star Nicola Amoruso admitted he dived and duped the ref to earn the Italians a last-minute penalty in the Stadio delle Alpi in September 2001.
The striker then slotted home the spot kick to give the serie A cracks a 3-2 win in Celtic's first outing in the group stages of the Champions League.
O'Neill said the decision still irked him. The Irishman said: "It still rankles, no question about that. To this day I still believe not a soul in the ground looked for it to be given.
"I remember turning away, waiting for the goal kick to be taken, and just being stunned. Absolutely stunned.
"There is no question that even after all these years that it is still there, that there is still a sense of injustice about it."
O'Neill's anger resurfaced after Amoruso confessed at the weekend that he had fooled referee Hellmut Krug.
He said: "I do admit it was definitely not a penalty," Amoruso said this weekend.
"I had only been on the pitch for a few minutes, there was one ball in the box, and the Celtic player was near me. It was never a penalty, but the referee gave me the decision and I scored it."
It was a decision that cost Celtic dear. The club failed to qualify for the latter stages of the competition that season, despite finishing their maiden campaign with an impressive nine points.
And even all these years on, the simmering anger over the decision has never left O'Neill and current Celtic manager Neil Lennon.
At a Hampden lecture last season given by former Juve boss Marcello Lippi, who was in charge of the Italians in 2001, Lennon was quick to remind him of Amoruso's tumble.
O'Neill added: "That game in Turin was our first Champions League game. Our original first match, which was due to be played at Celtic Park against Rosenborg on September was postponed because of the 9/11 tragedy in America.
"It really left a sour taste and I do have cause to wonder about it."