The couple got engaged on Theroux's 41st birthday in August 2012.
"She had included her friends and seemed excited about the process," people.com quoted a source as saying. The source also added that "Jen said she needed to focus on work".
Aniston, 44, who was previously married to Brad Pitt, is no longer enthralled by the idea of having children.
"There was a lot of baby talk in the past, but she is not focused on it. She's aware her age makes it more difficult. Her attitude is, 'If it happens, great, but if it doesn't, it wasn't meant to be,'" the source said.