The two have only been dating for three months and made their red carpet debut at the Emmy Awards and a pre-show party over the weekend, according to Us.
Sweeting, 26, reportedly popped the question on Wednesday. Cuoco, 27, tweeted Wednesday: "Flying high, I could literally touch the sky with you.... "
Neither has been married before. Cuoco was previously engaged to addiction specialist Josh Resnik, but the pair called off their engagement in 2012.