Two-match ban means more woe for Wenger
The disciplinary board of European football's governing body also fined the English Premier League club 10,000 euros "for improper conduct by its officials" during last week's play-off round first leg which Arsenal won 1-0.
Frenchman Wenger was banned from that game for his behaviour in last season's round of 16 tie at Barcelona but television pictures showed him sitting in the stands and talking on a mobile phone in the first half, apparently passing instructions to the bench.
"Disciplinary regulations stipulate that a manager may not communicate with his team during a fixture for which he is suspended and may follow the game from the stands only," UEFA said.
Arsenal are planning an appeal.
Wenger said last week he was confused over the rules.
"It was difficult because you didn't really know what the rules were. It was a bit confusing. It is a real concern because up to what level can you stop someone doing their job?" he said.
Wenger's latest suspension is a further blow for Arsenal who have taken part in the Champions League group stage for 13 seasons but could see that run ended on Wednesday.
The London club have been hit by recent injuries and the sale of captain Cesc Fabregas to Barcelona.
They have also taken only one point from their first two Premier League matches although that would pale into insignificance if they missed out on qualification for the Champions League.