The 33-year-old actress, who has starred in the U.S. TV series as Penny since 2007, took to Instagram to share numerous emotional pictures following the script-reading session ahead of filming the episode, due to air on 16 May.
One showed a close-up of the script, which Kaley captioned, "Yea, didn't sleep . @bigbangtheory_cbs."
A few hours later, the blonde screen star shared a snap of herself in floods of tears, writing, "Post table read for @bigbangtheory_cbs finale episode."
Courteney Cox, who starred in TV show "Friends" from 1994 to 2004, was quick to offer a message of support, commenting, "Awww I remember that feeling. And you guys have been together even longer."
Lastly, Kaley posted a picture of a load of screwed-up tissues that she had used to mop up her tears during the table read.
"Prepare yourselves ... for a finale that has truly given me a loss for words. Our whole universe .... @bigbangtheory_cbs," she wrote.
Kaley wasn't the only member of "The Big Bang Theory" cast to remember the occasion on social media.
Sharing a group picture of the cast and series writers, Melissa Rauch, who plays Bernadette in the show, wrote, "About to go into our table read for the series finale written by this group of geniuses - AKA: the heart and soul of @bigbangtheory_cbs.,People often ask what the secret is behind the success of the show...well, it's no secret...it's the sheer brilliance of these incredible minds. Love them all so very much."
Meanwhile, Mayim Bialik shared a picture of herself and Melissa, and captioned it, "His lady and I have been through a lot together as the new kids on the block of season 3 of @bigbangtheory_cbs . We have cried together and laughed together and raised kids on a set together. I couldn't have made it without her with any semblance of sanity. Thank you @themelissarauch for being you."