The actress, 32, and professional equestrian Karl, 26, confirmed the happy news by sharing a short clip to his Instagram account, showing Kaley sobbing with happiness almost immediately after the moment took place.
'Honey? How do you feel, honey? What's on your finger, honey?' Karl is heard asking his new fiancée from behind the camera.
'We're engaged!' a visibly emotional Kaley exclaims, although Karl is quick to quip back: 'You still haven't said "yes" yet.'
'Yes! I say yes! I say yes!' she replies enthusiastically.
In the caption alongside the sweet film, Karl wrote: 'Well after nearly two years I finally got up the courage to ask her to marry me.'
'This is the best night of my life and I think the video shows it is the best night for kaley as well.....of she said yes!!!!!'
He also shared an image of the stunning diamond ring he'd used to pop the question to Kaley, adding: 'I am so so so happy. Thank you @nadis_diamonds for making the greatest ring I could hope for. Absolutely brilliant. Thank you thank you.'
In life, there is nothing like dancing right after getting engaged. The purity and grace of the moment are inexplicable, it is truly as though life were a balloon bouncing on the smoothest zephyr. Honey; all I want is to be a balloon bouncing, bobbing, and flowing through life together. You are my everything @normancook
Fans have rushed to congratulate the evidently very happy couple on their news, with one writing: 'Omg legit crying here 😢😭 so happy for you both congratulations 🎉.'
'You two are so adorable 😍,' said another. 'Love your relationship 😊 You two are goals! Always stay like this! I wish you a lot of love and happiness all the time!'
The wedding will be the second marriage for Kaley, who finalised her divorce from her first husband, tennis player Ryan Sweeting, last May.
'Kaley Cuoco and Ryan Sweeting have mutually decided to end their marriage,' a representative for the couple stated at the time.