McManaman has put pen to paper on a three-and-a-half-year deal and joins an Albion side rejuvenated under the guidance of Pulis, who took charge at the start of the month.
The 23-year-old made 109 appearances in total for Wigan, helping the Lancashire club win the FA Cup in 2013 following a stunning Wembley upset against Manchester City.
"I'm really made up to have joined," said McManaman.
"When the chance came to move to West Bromwich Albion, and return to the Premier League, I couldn't turn it down.
"This is a great move for me and I hope the Albion fans will get to see the best of me.
"Albion are a great club, with a good tradition. I can't wait to get going."
McManaman is latest high-profile player to leave beleaguered Championship club Wigan, who are eight points from safety and rooted in the relegation zone.
Ben Watson, Shaun Maloney and Adam Forshaw have also departed the DW Stadium this month.
