A worker found the noose hanging from the one-story building Friday morning. Police took it down, but employees called the act "sickening."
"This looks like an attempt to intimidate working families in the county. This falls far short of accomplishing that," said Tefere Gebre with the Orange County Labor Federation.
The federation represents more than 90 unions.
The Los Angeles Area Office of the Council on American-Islamic Relations has also condemned the incident.