The Ireland lock was handed a two-week ban after being found guilty of punching Welsh opposite number Robert Sidoli in Saturday's defeat at the Millennium Stadium.
But the verdict dates back to the March 19, the day of the game, and leaves O'Connell available to line up for Munster against Biarritz on April 3.
"I am both relieved and happy that the process is now over and the hearing that I received was fair in its decision," O'Connell said.
Munster coach Alan Gaffney had questioned why O'Connell was cited for his part in the incident in the first place.
O'Connell explained afterwards that there had been "no malice or wilful intent".
He said: "Robert Sidoli and the referee accepted this in good spirits and once we shook hands, we both got on with it."
But the three-man Independent Disciplinary Committee - which was chaired by Lorne Crerar (Scotland) and included Jeff Probyn and Bob Taylor (both England) - heard the citation at Heathrow and found O'Connell guilty of punching.
After the hearing Irish Coach Eddie O'Sullivan said: "The two week suspension that Paul received I believe is a fair outcome in terms of what took place during the incident. It was a fair hearing and both he and I are happy that justice has been done."