The rep said that Aniston only removed the eight-carat radiant cut diamond sparkler to get it cleaned, reported Ace Showbiz.
"Everyone should calm down - the ring was being cleaned and is back on her hand," the rep said.
Aniston, 45, and Theroux got engaged in August 2012, but they are in no rush to get married.
"We just want to do it when it's perfect, and we're not rushed, and no one is rushing from a job or rushing to a job. And, you know, we already feel married.
"We have yet to set any dates. There have been no canceled weddings. There have been no postponed weddings. There have been no arguments about where to get married. Just clearing all that up," she had said.