Devils general manager Lou Lamoriello announced the deal during a conference call, hours before a league deadline for players under contract in Europe to sign in order to be eligible to play in North America in the upcoming season.
Lamoriello says Larsson, the top defenseman chosen in the draft, received a signing bonus but not any individual rookie bonuses.
"Getting a young player to understand and agree to (no rookie bonuses) and also his representation, this young man is as mature as he can get at his age," Lamoriello said of the 18-year-old Larsson. "He made a decision to forego all of those bonuses to get this signed, to get his career under way and to become a Devil and just get ready for training camp
Larsson will likely play in either the NHL or AHL this season.
"If that's the best thing for his development," Lamoriello said. "If we thought that something else was, then we'd do that, but it's our intention and it's his intention to be in North America."
Larsson is the fifth player chosen in the first round to reach a deal with his new team.