Tristan Thompson is opening up for the first time about his mother's unexpected death ... penning her an emotional tribute letter on Instagram, writing his "soul is empty" since her passing.
"Dearest mommy in heaven, It has been one month since you’ve been gone," the former NBA player wrote.
"I’m in disbelief. I'm in the deepest part of sorrow & grief. My soul is empty as I come to terms that my biggest supporter/superhero is gone."
The 31-year-old continued, writing about the sacrifices his mom made for him and his siblings.
"Mommy, all the sacrifices you did for ur sons will never go unnoticed or without appreciation. You were an amazing mommy, role model, best friend & the strongest woman I know."
Thompson also touched on some of the public mistakes he's made as an adult, vowing to show his mom raised a good man.
"Im sorry mommy for the wrong decisions Ive made in my life. Im sorry for the embarrassment &pain. You raised me better than what I was able to show you," Tristan wrote.
"But I have also learned sorry is not enough. Actions speak louder than words. So I wont just say sorry. Stay tuned to the ways I will show the world what an amazing son you raised."
Fans, NBA stars, and celebs flooded Thompson's IG comments with support, including his former teammate LeBron James and Kim Kardashian, who left a heart and dove emoji.
Of course, Kim's sister Khloe -- who shares two kids with Tristan -- and the Kardashian family have been by his side since his mom, Andrea, suffered a heart attack at her home in Toronto on Jan. 5.
Khloe, who is no longer romantically involved with Thompson, even took a private jet to Toronto the day after Andrea passed to comfort him. The Kardashian family also attended her funeral.