Barrymore's publicist confirmed the engagement Friday. The couple were reportedly engaged over the holidays in Sun Valley, Idaho. It will be the actress' third marriage.
Us Weekly first reported the engagement. A photo of the pair, in which Barrymore sports a diamond ring, was released to People magazine.
The 36-year-old Barrymore was briefly married to Jeremy Thomas in 1994 and to comedian Tom Green in 2001.
Kopelman is the son of former Chanel CEO Arie Kopelman.