To his co-stars, he writes, "You are all my playmates that I have fallen in love with."
While the actor -- who has picked up four Emmy Awards playing Sheldon Cooper on the CBS sitcom -- didn't allude to Entertainment Weekly's report he was ready to step away from the show, he said the reality of the show's end date hasn't really sunk in.
"It has hard (nearly impossible) to really accept that this is a picture of the first of the final 24 episodes we will shoot for The Big Bang Theory," he wrote in a lengthy Instagram post alongside a photo of him with costars Johnny Galecki, Mayim Bialik, Melissa Rauch, Kunal Nayyar, Simon Helberg and Kaley Cuoco.
"I feel very fortunate that we have another 23 episodes to shoot this season because I am hopeful that with each and everyone, my level of REALLY accepting this fact will sink in," he continued.
"Something else I feel grateful for -- and this gratitude needs no time to 'sink in' or become more 'realized;' this grateful-feeling is always with me bit is multiplied in this moment of us announcing our final season -- but I feel such intense gratitude for our devoted viewers who are the ACTUAL reason we have been graced with the opportunity to explore these characters for 12 years of our lives," Parsons added.
After thanking the crew and writers, he turned to the cast.
"You are all my playmates that I have fallen in love with and who have become a part of my life on set and off. You are my playmates when we don't feel like playing but have to because it's our job to get out there and communicate and pretend we're these other fictional people and we look into each other's eyes and say these words and end up creating this weird, other reality that has enriched my life more than I will fully ever understand," he wrote. "I will miss all of you and all of this more than I can say and more than I can know at this time."
Read Jim's full note below: