Striker had looked likely to join Leicester City in January, instead signed a new deal at Leeds, but has now moved to Goodison Park
Jack Harrison is having a medical at Everton after they triggered his release clause at Leeds. Initially, he will arrive on Merseyside on a loan.
Harrison, 26, signed a new five-year deal at Elland Road in April but the terms included a clause that can be triggered by clubs following relegation from the Premier League.
The former Manchester City forward has missed the start of the Championship season with a hip injury and he has been unable to help Leeds in their opening two matches: a draw with Cardiff City and a defeat to Birmingham.
He was subject to a bid from Leicester City in the January transfer window only for the move to collapse dramatically. Harrison subsequently agreed fresh terms at Leeds.