"I asked. She said yes!!!" Astin, 28, wrote as he shared a pic on Instagram that showed him and Camp, 33, smiling as she showed off her sparkling engagement ring.
The True Blood alum also shared the photo on Instagram, writing, "He asked. I said YES!!!!" The couple have been vacationing on the Hawaiian island of Kauai.
As Us Weekly previously reported, the pair made their first public appearance as a couple in June 2013. At the time a source told Us that the pair had known each other for a while before they costarred in the hit 2012 film.
"They met through mutual friends and then worked together," the source said, adding that they were initially friends but it turned into something more after Camp split with her husband of three years, actor Michael Mosley, in April 2013.
Camp and Astin "have amazing chemistry," the source added.
Want stories like these delivered straight to your inbox? Sign up now for the Us Weekly newsletter!