The 32-year-old confirmed the news at the Grove in LA, where she helped unveil the Make Up For Ever Remix Make Up Bag and Make Up For Ever Mobile Tour.
The couple, who met on the sets of TV series 'Pan Am', first went public with their relationship in February 2012, reported Us magazine.
Last October, Ricci was spotted wearing what appeared to be an engagement ring but had declined to comment on engagement speculation.
But she has finally confirmed the news. "Yeah. We got engaged a couple months back," she said.
Earlier, Ricci had called off her engagement to actor Owen Benjamin in 2009, saying, "My ideal man was somebody smart and funny that I love being with. I've always said to people you should never let anyone change who you are because the only commodity you really have is your individuality."