It occurred late in New York's 45-12 romp on Monday Night football.
The source said Haynesworth, a 350-pound defensive tackle, received a $10,000 fine for the on-field skirmish, and Jacobs, a 264-pound running back, was fined $7,500.
"I guess they did," Jacobs told the Newark Star-Ledger Wednesday when asked about the fine. "But that was expected. I was just trying to protect myself."
Haynesworth, who rarely speaks to the media, had no comment nor did any Redskins' officials.
The outcome left the Giants (8-6) in the thick of the NFC playoff chase, while the Redskins sank to 4-10 with the third loss in their last four games.