Report: Red Sox GM headed to Cubs
An announcement is reportedly expected to be made within the next 24 to 48 hours.
The news comes a week after the Cubs asked the Red Sox for permission to speak with Epstein about a role within their organization.
Epstein, 37, has one year left on his contract and one source said the Red Sox will want "something real" in return should he leave. That could mean a player, money or a combination of both, but it is unclear.
Epstein is two months away from his ninth anniversary with the Red Sox, in which time the team has won two World Series.
He became the youngest general manager in the history of Major League Baseball when he was hired by the team aged 28 in 2002. Boston broke an 86-year drought by winning the World Series two years later.
The Cubs have not won the World Series since 1908 — the longest drought in baseball.