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The 22-year-old was sent-off by referee Marius Mitrea for a tip tackle in their semi-final win over Leinster in Dublin.
A disciplinary panel decided, by a majority, that Evans "undertook a lawful tackle in a manner that was consistent with the laws of the game."
Uncapped Evans is available for Wales' June Tests against Tonga and Samoa.
The tackle on Leinster centre Gary Ringrose happened in the 38th-minute with Scarlets leading 21-10.
The Ireland international came down on his head as Evans and Scarlets prop Samson Lee stopped his progress.
The disciplinary panel, made up of Scotsmen Roddy Dunlop QC, Roddy MacLeod and Iain Leslie, decided the tackle "only became dangerous as a result of the intervention of Scarlets No 3 (Samson Lee)."
Scarlets wing Steff Evans can play in Saturday's Pro12 final against Munster after the red card he received against Leinster was rescinded.