The person spoke on condition of anonymity because the Giants have not announced the deal, which comes less than two weeks before the season opener against Jacksonville. He won't have to.
Kim Jones of NFL Network and WFAN confirmed that the deal is done.
Beckham's deal is worth as much as approximately $95 million and includes about $65 million in guaranteed money, according to the person with knowledge of the deliberations.
The scene was suspicious enough that one team reportedly wanted to do a background check on Beckham, thorough enough to make sure he wasn't using illegal drugs.
The 25-year-old Beckham was entering the fifth and final year of his rookie contract, with a base salary of $8.4 million. His guaranteed money sits behind only Matt Ryan ($94.5 million) and Kirk Cousins ($84 million), per Over The Cap. "And I'm just so happy that it is finally done now", he said.
Beckham had said early in training camp that he was taking a risk practicing without a new contract.
Beckham, coming off a season-ending ankle injury, has been deemed healthy this offseason, with the Giants targeting Week 1 to unleash their star receiver.
He topped 1,300 receiving yards in each of his first three National Football League seasons before managing only 302 yards in four games in an injury-shortened 2017 season.