The comedian, 40, helped ring in Theron's birthday with some of her other famous friends, including John Krasinski, who was spotted outside the party.
Earlier in the week, Handler, Krasinski and his wife Emily Blunt attended Aniston and Theroux's surprise nuptials. The former late night host accompanied the couple to a Los Angeles-area airport before they took off for their exciting Bora Bora honeymoon, but apparently did not join.
Aniston and Theroux's travel buddies included maid of honor Courteney Cox and the actress's repeat costar Jason Bateman.
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Handler spent most of the past week with her furry friends Jax and Chunk. The outspoken star has shared several photos of the adorable pets on her Instagram.
"My big fat baby," she wrote, posting a picture of Chunk wearing a bandana with a tennis ball in sight.
Prior to Aniston's backyard wedding, Handler also shared a photo with Chris McMillan, the Cake actress's longtime hairstylist.
"This little doozy cuts my hair," Handler wrote.
There may be a reason that Handler didn't attend Aniston and Theroux's friend-filled honeymoon, she had previously joked on Instagram about running out of space for visa stamps on her passport.
The comedian shared a screenshot of an email with her assistant, who said she would be able to get additional pages for her passport on Friday afternoon but was nervous because it's "so close to when you leave."
Handler wrote, "An email from my asst this morning. This is how I know I am living my life."