Youssouf Mulumbu has committed his future to the club after signing a two-and-a-half year contract, plus a year in the club's favour.
The deal, which is his second updated contract in the space of seven months, is reward for his excellent performances on the pitch.
The 24-year-old has been instrumental in Albion's success this season with a number of eye-catching performance in the middle of the park.
Baggies boss Roberto Di Matteo - a former midfielder himself - was pleased that midfield enforcer would be part of his future plans.
"I'm delighted Youssouf has signed his new contract, which is fully deserved," said the Italian.
"He's had a very good season so far and is a player who wants to learn.
"He's a big favourite with the fans and I think that is down to the fact they recognise he has a specific role here.
"He does a little bit of the dirty work for the team and is a player who gives us balance.
"He also chips in with some goals, which aren't expected but are a bonus!
"We're all looking forward to carrying on working with Youssouf for years to come."