"I've done nothing wrong and I have nothing to hide," Manning told reporters on Thursday in his first public comments on the matter.
The two-time Super Bowl-winning quarterback turned over a potentially incriminating email earlier this month in connection with a lawsuit that alleges Manning, the Giants and a team equipment manager knowingly provided memorabilia that was not worn in games.
Manning, 36, claims that the emails were "taken out of context" and that he's "more angry than anything" that his character is being called into question.
He said the pending litigation barred him from going into specifics.
"I will say that I've never done what I've been accused of doing," Manning said. "I have no reason, nor have I ever had any reason, to do anything of that nature. ... And I know that when this is all done, everybody will see it the same way."
The lawsuit, first filed in Bergen County Superior Court in New Jersey by collectors Eric Inselberg, Michael Jakab and Sean Godown three years ago, is to go to trial on September 25.
The lawsuit alleges an elaborate scheme to produce, pass off and sell memorabilia as game-used that was not.