Bielik, 27, has agreed a three-year contact and checks into The Hawthorns for a fee reported to be in excess of £1million.
The Poland international, who is most at home in the centre of defence but can play in defensive midfield, becomes Albion’s fourth new signing of the summer.
He offers important competition and cover following the imminent sale of star defender Torbjorn Heggem to Bologna for a deal worth up to £10m.
Bielik joins central defensive options including Nat Phillips and George Campbell – two other summer recruits – and academy graduate Caleb Taylor.
Ryan Mason’s Albion are also hopeful of completing a season-long loan move for Manchester United midfield prospect Toby Collyer.
Mason told the press at Thursday’s pre-Wrexham press conference he was confident Albion would end the summer transfer window with a squad capable of being competitive in the Championship this season.