The 36 year-old Hollywood actress and Kopelman have been romantically linked since February last year.
Drew's publicist apparently confirmed the news to People magazine as well as issuing a photo of the loved-up pair showing Drew flashing her new rock.
The couple are said to have got engaged in Sun Valley, Idaho, during a romantic Christmas break, according to the US gossip magazine.
It is thought art consultant Kopelman went down on bended knee with a colourless radiant-cut diamond ring by Graff, weighing just under 4 carats.
Though the pair have never confirmed their relationship, they have been spotted out looking cosy together numerous times, leading to speculation they were more than good friends.
They apparently dated briefly in 2010 but split as their relationship wasn't working before reuniting the following year.
Drew will be hoping this is a case of third time lucky with Will, who is the son of former CEO of Chanel Arie Kopelman, as she already has two failed marriages under her belt.
The E,T. child star married bar owner Jeremy Thomas in 1994 but filed for divorce just two months later.
Another short marriage came when she tied the knot to comedian Tom Green in 2001, but the marriage failed to go the distance and ended just five months later when Green filed for divorce.
Drew was also engaged twice before – to Leland Hayward when she was 16 and the following year to musician Jamie Walters. Neither engagements ended in marriage.
