The goalkeeper was dismissed shortly before half-time in Wednesday's Champions League last-16 first-leg tie at the Emirates Stadium, when he was adjudged to have denied Arjen Robben a clear goalscoring opportunity.
Szczesny will definitely miss the return leg at the Allianz Arena because of the red card, though he could face a lengthier ban if Uefa decide to review the incident.
Arsenal manager Arsene Wenger was visibly frustrated with the decision, while Szczesny expressed his thoughts before walking down the tunnel.
And Wenger confirmed the Poland international will be sanctioned by the club.
"It was frustration but we are professionals, me included, and we have always to master our reactions," he said.
"Wojciech is part of that as well. We'll deal with that internally. We don't agree with that."
Szczesny is available for Arsenal's fixture with Sunderland at the Emirates Stadium on Saturday.