Greenwood, who was rated highly by former Leeds boss Jesse Marsch, is not in Daniel Farke’s plans for the season.
He is now being shipped out on a season-long loan deal and is heading to Leeds’ Championship rivals Middlesbrough.
Greenwood will be looking to play on a regular basis under Michael Carrick in the north east and help Boro mount a promotion push.
It is unclear whether there will be any option in the loan to let Middlesbrough keep Greenwood on a permanent basis.
Greenwood made 18 appearances in the Premier League for Leeds last term and scored against Bournemouth.
The Sunderland-born midfielder is capable of playing as both a central and attacking midfielder, as well as on the flank.
He has played just once in the Championship, with most of his game time coming in the Premier League.
