The Mentalist star was holidaying in Rio de Janeiro, Brazil when her boyfriend popped the question - and she said yes.
Tunney tells UsMagazine.com, ""The diamond was from his grandmother Mimi's engagement ring... It means so much that it was his grandmother's. She had a long and happy marriage to his grandfather. I like to think it's good luck!""
Marmet's holiday proposal was actually his second attempt to make Tunney his wife, after a bout of illness on the trip scuppered his first try.
Tunney reveals, ""He'd made an earlier attempt at the beach in Bahia, but I had what I thought was Dengue Fever and I threw up over his shoulder when he was about to take the ring out. Mercifully, I recovered and was healthy enough to accept the second time.""
Tunney was previously married to producer/director Bob Gosse from 1997 to 2002.