The pair competed together on Season 12 of the show back in 2011, placing second, before they were reunited for the all-stars season the following year. The duo was eliminated seventh on their second go-around.
"My dearest Kirstie, We haven't spoken lately and I'll tell you everything when I finally see you, but for now I want to say that I love you very much and I wish you the most peaceful rest," Maksim shared following news Alley died Monday after a battle with colon cancer. She was 71.
"You were one of the most unique people I have ever met and easily one of the brightest moments of my personal and professional life," he continued. "Some of our relationship is heavily documented. Most of it is known to select few. All of it was like a wild rollercoaster."
"From Maude to DJ Lil Buttercup you were always all in for life. As I'm typing this, memories of our time together rush to my head, I remember how absolutely wild you were and I start to tear up. Something you'd absolutely hate," he added. "And now I can't help but smile because I remembered exactly what you wanted me to say at your funeral. Don't think I can do it here."
He concluded: "I thought you'd be around forever. I wish we spoke often. Thank you for everything. I love you Kirstie Alley. RIP."
In 2014, Chmerkovskiy opened up to Andy Cohen about his strained relationship with Alley on "Watch What Happens Live," claiming Scientology was to blame for things souring between them.
"We had a great relationship ... but I got a message now that I am associating with other people that she can't be associated with, I am no longer to be spoken with, and sorry, but it is what it is," he said, likely referring to his friendship with ex-Scientologist Leah Remini.
"I'm Jewish. I don't really believe in science fiction, but whatever," he said at the time. "It's sad that we've gone through so much together, and I feel like I've helped her. And this is where we're at now. But I think the world of her, and I wish her the best."
Alley responded at the time on Twitter, writing, "Dear Sir..after you have ass raped me there is really no reason to include 'I wish you the best'.. It's rhetorical."
"You can thank [my friendship with] Leah Remini for that," he clarified. "A note was sent to a friend telling me I was 'disconnected,' as in, I am no longer allowed to be Kirstie's friend. I find it ridiculous for an adult human being to 'disconnect' from someone. But everyone is entitled to their own insanity."
Maksim, Alley and Remini all got into it on social media earlier this year over the situation in Ukraine, after Alley tweeted about the conflict which you can read about below:
Alley's children True and Lillie Parker confirmed her death Monday on the actress' social media pages.
"To all our friends, far and wide around the world ... We are sad to inform you that our incredible, fierce and loving mother has passed away after a battle with cancer, only recently discovered," they wrote.
"She was surrounded by her closest family and fought with great strength, leaving us with a certainty of her never-ending joy of living and whatever adventures lie ahead," the pair continued. "As iconic as she was on screen, she was an even more amazing mother and grandmother."
Adding they were "grateful to the incredible team of doctors and nurses at the Moffitt Cancer Center for their care," Alley's children said their mother's "zest and passion for life, her children, grandchildren and her many animals, not to mention her eternal joy of creating, were unparalleled and leave us inspired to live life to the fullest just as she did."
"We thank you for your love and prayers and ask that you respect our privacy at this difficult time," the statement concluded.
See more celebrity tributes for the Emmy Award-winning actress below: