Kearney caught a high kick just after the hour mark at Thomond Park and was struck hard in the face by the 2009 Lions captain when the latter attempted to kick the 'loose' ball after Kearney had come to ground.
The 33-year-old second row wasn't punished by referee Nigel Owens, who didn't see the incident that rendered Kearney unconscious, but he could have faced retrospective action from the citing commissioner.
But instead, after reviewing video footage of the 62nd-minute incident, Eddie Walsh has decided that O'Connell has no case to answer.
A lack of intent appears to the reason behind that decision, with O'Connell now free to concentrate on Saturday's Heineken Cup showdown with Clermont Auvergne in Montpellier.
O'Connell was in fine form in the last round of European action as he guided Munster to a surprise win at English Champions Harlequins on April 7.
He has since been heavily tipped for a place in Warren Gatland's Lions squad for the summer trip to Hong Kong and Australia despite the fact that he has spent the vast majority of the season on the sidelines nursing a back injury.