Del Horno, 25, was red-carded against Barcelona for a challenge on Lionel Messi.
Chelsea appealed the severity of the decision and won.
Chelsea said: "Following the sending-off of Asier Del Horno against Barcelona, Chelsea FC were asked for our observations on the incident as part of the standard Uefa disciplinary procedure.
"In that submission we made a case that the offence of violent conduct was unjustified and that an automatic three-match ban as a result would similarly be unjust.
"There was no appeal against the dismissal itself as the Uefa disciplinary procedures only allow for a retrospective decision on the basis of mistaken identity, or if there was no contact between the two players.
"After our submission, Uefa analysed video footage of the incident and made the decision that the offence did not constitute violent conduct. It was decided that a three-match ban was not applicable."