O’Brien was cited after television footage showed his forearm clearly made contact with the face of All Blacks winger Waisake Naholo as the Irish loose forward joined a tackle in the 59th minute of the match at Wellington Regional Stadium.
Naholo was taken from the pitch for a concussion test, which he failed, forcing his replacement. Referee Jerome Garces, who had sin-binned Lions prop Mako Vunipola minutes before, took no action on the pitch.
The Ireland flanker was charged by citing commissioner Scott Nowland after the game but New Zealand Rugby (NZR) said on Sunday he had been cleared.
“Having conducted a detailed review of all the evidence available, including all video footage and additional evidence from the player and submissions from his legal representative Max Duthie, the Independent Judicial Committee dismissed the citing complaint,” NZR said in a statement.
The committee had earlier banned All Blacks centre Sonny Bill Williams for four weeks after he was shown a red card for a shoulder charge on Anthony Watson in the 25th minute of the match.
O’Brien has played both tests for the Lions on this tour and his contribution in the second test had earlier been praised by assistant coach Graham Rowntree who described him as ‘outstanding’ and the benchmark for the team’s performance.
“Right to the end of the game he is the barometer for us with his energy,” Rowntree said. “His aggression and ball pressure, his tackling, his carrying. I think he has been outstanding.”
Lions coach Warren Gatland said he was pleased with the committee’s decision, while O’Brien said: “Firstly, I hope Waisake is okay. I’d like to thank the panel for carefully considering the case.”
(Reporting by Greg Stutchbury; Additional reporting by Neil Robinson; Editing by Clare Fallon)