Irish-born make-up artist Cathriona was found dead by friends at her LA home last week. She was only 30.
Jim was one of hundreds of mourners who attended Cathriona's funeral at the Our Lady of Fatima church in Cappawhite, Co Tipperary, on Saturday (10 October).
The 53-year-old helped her grieving family carry her coffin through the town during the highly emotional farewell service.
He was seen looking visibly upset during the proceedings.
After the ceremony, Jim returned to Twitter to post a moving message in honour of his former lover.
Alongside an artistic portrait of them both in shadow, he posted a red rose emoji and wrote: "Love cannot be lost."
Love cannot be lost. pic.twitter.com/XxPYOhkdzc— Jim Carrey (@JimCarrey) October 10, 2015
His 15.2 million followers were quick to send messages of support to The Mask star, with one saying: "Stay strong Jim!"
Another said: "You've made so many people happy, including me. I'm very sorry for your pain."
A sympathetic soul wrote: "@JimCarrey my heart goes out to you during this difficult loss! May you find your laugh again soon and find peace in your heart!"
One more said: "I'm so sorry, Jim. My heart is breaking for you. Sending you all of my love. Stay strong."
On Tuesday (29 September), the Hollywood actor released a statement about the death of Cathriona.
He said: "I am shocked and deeply saddened by the passing of my sweet Cathriona.
"She was a truly kind and delicate Irish flower, too sensitive for this soil, to whom loving and being loved was all that sparkled. My heart goes out to her family and friends and to everyone who loved and cared about her. We have all been hit with a lightning bolt."
Cathriona's final tweet was posted on 25 September and read: "Signing off Twitter, I hope I have been a light to my nearest and dearest. [Love] to you all."
Multiple outlets allege that Cathriona took her own life.
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