The unnamed steward was removed from the Liberty Stadium after the incident at the 2-1 win against Manchester United on Saturday.
The steward in the United end goaded home fans with Cardiff's head-tapping "Ayatollah" after Swansea had scored.
Swansea Stadium Management Company said the steward had been employed by an external security agency.
"The steward in question was removed from the stadium immediately and was spoken to by the police on duty," said a stadium spokesperson.
"He will certainly not be utilised by us again, while we also understood he is no longer employed by the agency in question."