Blagbrough, 19, made his Super League debut for the Giants last season against Bradford and came through the ranks at the Giants’ academy where he recently won the Under 18’s Academy Player of the Year Award.
Eagles Head Coach Mark Aston said: “It’s great to announce Jack is joining the club, he’s an exciting young player with a bright future.
“He’s a big, strong player that, let’s say, won’t be afraid to straighten a few collars! He’s the type of player I’m keen to sign and we are known for bringing to the club, young players with a great attitude and work ethic who have spent time in great systems.
“He’s a smart kid and will continue to study Mathematics and Biology at the University of Leeds alongside his development here and I have no doubt he’ll get better and better over the next few years.”