West Brom head coach Valerien Ismael has made out-of-contract Barnsley captain Alex Mowatt his first signing.
Mowatt was a key man for Ismael last season, playing 44 Championship games as the Tykes reached the play-offs.
"Alex put his performances on the next level. He is an outstanding player with outstanding qualities and mentality," Ismael told the club's website.
"He scores goals outside the box and on set-pieces he is very dangerous.
"He is a leader as well. He is still a young guy but he has a lot of experience. He has hunger and he is the exact profile of player that suits West Bromwich Albion.