The couple announced their separation in September 2015 after two years of marriage.
"Grammy Party ..... Feeling great. Lovely night," she captioned one snap.
Neither Avril nor Chad wore their wedding rings though, so it could be that they are just very friendly exes as they have also been working on music together since their split.
Sk8er Boi singer Avril took to Instagram to reveal her split from Nickelback rocker Chad back in September.
"It is with a heavy heart that Chad and I announce our separation today... Through not only the marriage, but the music as well, we've created many unforgettable moments," she told fans. "We are still and forever will be, the best of friends, and will always care deeply for each other. To all our family, friends and fans, thank you sincerely for the support."
Avril was previously married to Sum 41 rocker Deryck Whibley.
Chad and Avril were just one of the stunning celebrity pairs to attend Clive's party. Pregnant Chrissy Teigen showed off her curves in an eye-catching emerald green dress as her husband John Legend placed a tender hand on her burgeoning bump.
Christina Aguilera also went for a form fitting look in a black gown as she posed alongside fiance Matthew Rutler, while Gwen Stefani looked incredible in a flirty red number as she cuddled up to boyfriend Blake Shelton inside the bash.
Other famous faces at the annual bash included Ciara, Ellie Goulding, Meghan Trainor, Lana Del Rey and Jordin Sparks, while former One Direction bandmates Zayn Malik and Harry Styles enjoyed something of a reunion at the event.