Pac-12 Commissioner Larry Scott announced Kiffin had been fined $10,000 for criticizing officials after Saturday's triple-overtime, 56-48 loss to Stanford, and for doing so again Sunday.
Kiffin asserted the game officials should have allowed USC to attempt a potential game-winning field goal at the end of regulation time, the Los Angeles Times reported.
"The Pac-12 has specific rules that prohibit our coaches from making public comments about officiating, and this prohibition specifically includes comments that create doubts about the credibility of the Conference's officiating program," Scott said in a statement.
The conference also suspended Trojans safety T.J. McDonald for a half for making a late hit during the game.
"Mr. McDonald had been previously warned about illegal hits above the shoulders on defenseless opponents," Scott said.