"The good news is that was probably the most -- I'm choosing my words really carefully -- it was kind of the most gentle separation, in that there was no animosity," Theroux told The New York Times in an interview published Saturday.
"Again, neither one of us is dead, neither one of us is looking to throw hatchets at each other," he added. "It's more like, it's amicable. It's boring, but, you know, we respected each other enough that it was as painless as it could be."
The couple had been together for seven years -- and married for two -- when they announced in February that they had split up, People magazine noted.
Theroux, 47, told The Times he and Aniston, 49, remain friends.
"It was heartbreaking, only in the sense that the friendship would not be the same, as far as just the day to day," Theroux said. "But the friendship is shifting and changing, you know, so that part is something that we're both very proud of."
Best known for his performance in the HBO drama The Leftovers, Theroux will soon be heard voicing one of the titular dogs in a new version of the animated movie Lady and the Tramp, opposite Tessa Thompson.