The 48-year-old star initially did not mind his facial hair, but quickly grew tired of it and asked him to shave.
"She likes it, up to a point. She'll like it for about a month and then she's like, 'OK, you have to get rid of it.' Then I'm like, 'No, I actually have to keep the beard now for the whole show," Theroux, 45, said during his appearance on "The Ellen DeGeneres Show".
"The first season I had to have stubble for the entire season and that was torture for her. (But) now it's soft," he added.