The ex-Huddersfield Giants front-row has joined on a two-and-a-half year deal and joins with immediate effect.
Chester worked with Walker previously at Hull KR and rates him highly.
Admittedly, the 26-year-old has failed to earn a regular place with Saints since joining from Rovers at the end of last season but will now offer more punch for Trinity who already boast the likes of Craig Huby, David Fifita, Anthony England, Mitch Allgood and Keegan Hirst up front.
Chester, whose in-form side host Huddersfield tomorrow, said: “I have worked with Adam (Walker) for a number of years, and we have got a good relationship.
“He is one of the best young British forwards in Super League and we have beat off a host of other Super League clubs for his signature.
“I would like to thank St Helens and Michael (Carter) for making this deal happen and I am sure he will become a fans favourite at the club for many years.”
Walker, who has a chance of coming into the squad for Monday’s game at champions Wigan Warriors, said: “I am looking forward to getting out there.
“I have known Chris most of my professional playing career; I met him when I played for Scotland about six or seven years ago and know what to expect from him and he knows what to expect from me, so I am looking forward to playing under him again.”
Having signed a two-year deal with Saints, the Bradfordian actually made his debut against Trinity in February and played eight games since but none since the loss at Warrington three weeks ago.
Wakefield chairman Michael Carter said: “ I am delighted that we have managed to secure Adam for the next two- and -half years.
“I’d just like to thank Eamonn McManus and Mike Rush at St Helens and Martin Shuttleworth, Adam’s agent, for concluding this deal quickly. Our squad is shaping up very nicely for this season and beyond.”