The Maniac star took to Instagram on Monday to wish his ex-wife a happy 50th birthday, a year after the two announced their split following two years of marriage.
"Happy Birthday to this fierce Woman. Fiercely loving. Fiercely kind. ....and fiercely funny. ❤️ you B," the 47-year-old actor captioned a pic of his former flame with toned arms holding up a pair of horns.
The sweet gesture comes after Theroux missed Aniston's milestone birthday party over the weekend, instead attending the Opening Ceremony Lunar New Year 2019 celebration for New York Fashion Week on Sunday.
Aniston and Theroux announced they were parting ways last year, just days after her 49th birthday. In October, a source told ET that both were doing well following the breakup.
"Since they split, her friends believe their plan to move forward in life without one another was the best decision for both of them," the source said at the time. "Neither of them is pining for each other but instead, finding themselves again."
"Breakups are never easy but [Aniston] truly has remained positive about the situation," the source said. "She has moved on. She feels she grew more as a person and learned more from her relationship with Justin than she has learned in any relationship in her life with a man."
Meanwhile, Theroux is not Aniston's only famous ex celebrating her big day. Brad Pitt actually made a surprise appearance at the Friends star's party, 13 years after their divorce.