The four-year-old golden retriever, who grew up on the set of Netflix's Full House reboot, died due complications in surgery.
The show's official Twitter announced the sad news yesterday (December 16).
Now, some of the show's stars have shared their own tributes to the late Cosmo.
See the heartfelt messages for him from actresses Candace Cameron Bure and Jodie Sweetin below.
We're sad to share that the Fullers' faithful dog Cosmo, who grew up on our set, passed away after complications from surgery. There will never be another quite like our boy. 💛 We'll miss him forever. pic.twitter.com/yVjkJONdQ9— Fuller House (@fullerhouse) December 16, 2019
Our sweet boy Cosmo is now running around in doggie heaven. I imagine he's playing with Comet 😉 right now.— Candace Cameron Bure (@candacecbure) December 16, 2019
Cosmo has been in Fuller House since the start and we are heartbroken that he passed away during surgery complications. You'll be so missed love bug ❤️@fullerhouse pic.twitter.com/xzqULFRF8s
As you may have heard, our beloved Cosmo has passed away. He had gone in for surgery and suffered complications. Our little Cosmo was always such a good boy and our hearts are 💔. Say hello to Comet for me, buddy. #brokenhearted #suchagoodboy #fullerhousefamily #alldogsgotoheaven #itsalwaysopen