"We reopened the investigation based on new info," the league explained in a text message. "Concluded there was a violation of our personal conduct policy and imposed 6 game suspension which he accepted without appeal."
Brown, who was released by the Giants last October and is not on an NFL roster, can begin serving his suspension this week, a source told ESPN's Dan Graziano.
Back in February, "Good Morning America" aired an interview with Brown,.
"I mean I had put my hands on her," Brown told ABC News' Paula Faris at the time. "I kicked the chair. I held her down. The holding down was the worst moment in our marriage. I never hit her. I never slapped her. I never choked her. I never did those types of things."
Faris asked Brown how people should reconcile his distinction between abusing his wife but never hitting her.
"They're not supposed to. What I did was wrong. Period," Brown said. "Domestic violence is not just physical abuse. We're talking intimidation and threats, the attempt to control, body language. An abuser is going to abuse to a certain degree to acquire some kind of a reaction. ...
"The world now thinks I beat my wife," he said. "I have never hit this woman. I never hit her. Not once."
Brown was charged with fourth-degree domestic violence in May 2015. The league suspended him for the first game of the 2016 season. Giants owner John Mara defended Brown in August. After the suspension, Brown appeared in five regular-season games but landed on the commissioner's exempt list in October after the NFL obtained new evidence released by law enforcement.
Meanwhile, the league's decision to suspend Brown six games comes on the same day the Cowboys await word from a U.S. District Court judge in Texas on if running back Ezekiel Elliott will be granted a temporary restraining order that would allow him to continue to play this season. The league recently suspended Elliott for six games for domestic violence accusations.
The league maintains that announcing Brown's punishment in light of Elliott's situation is purely coincidental.
"Timing has nothing to do with Zeke and made no sense to hold this until Zeke was complete," the NFL said in a text to ESPN.