The 19-year-old younger brother of Plymouth’s vice-captain Todd Kurtz is the replacement for Charlie Gjedde, who quit British speedway at the end of April.
Brady Kurtz spent the last two seasons racing for Somerset in the Premier League and joined Poole in the Elite League this season.
Devils team manager Lee Trigger said: “Brady has been a long-time target of mine even through the winter, but wanted to concentrate on racing full-time in the Elite League and also wanted to make his way onto the Polish speedway scene.
“I have been in talks with Brady for the last six weeks when it became apparent that Charlie was having doubts about continuing his British speedway career commitments.
“It was quite clear to me then that Brady was going to give the opportunity of more racing in the UK in the Premier League with the Devils some serious consideration.
“The negotiations with Brady have been very easy. He has a wise and professional head on his young shoulders and knows which direction his future lies.
“Signing Brady has put a massive smile back on my face and now we can continue our quest for a Premier League play-off position confident that we have a one to seven back in place very capable of achieving our ambition.
“I would like to take this opportunity to welcome Brady to Plymouth, where I am sure he will slot right into our team with the great team spirit that is already in place.
“My thanks go to Poole promoter Matt Ford for all his help and support in bringing Brady to Plymouth, without which this move could never have happened.”
Teams for Friday’s Premier League meeting at the St Boniface Arena.
Plymouth: Brady Kurtz, Kyle Newman, Jack Holder, Todd Kurtz, Sam Simota. Reserves: Stefan Nielsen, Ellis Perks.
Workington: Ricky Wells, Rasmus Jensen, Kenneth Hansen, Mason Campton, Claus Vissing. Reserves: Adam Roynon, Matt Williamson.