Wolves are happy to sell the player having reinvested in the squad this summer. The deal should see them net around £3 million with add-ons.
Douglas can now travel to Leeds to complete his medical examinations on Thursday.
He made 42 appearances for the club last season, but the 28-year-old was not deemed a key member of the team as they move up to the Premier League.
Douglas has a solitary cap for Scotland and he will be hoping that he can be a key player for Marcelo Bielsa's new look Leeds United.