Manningham has agreed to a one-year deal with the club, according to FOX Sports 1 NFL Insider Mike Garafolo and other media reports.
Known for his spectacular 38-yard reception that began the team's winning drive against New England in the 2012 Super Bowl, Manningham spent the last two seasons with the San Francisco 49ers. Those two seasons with the 49ers were cut short by injury. In 2012, he played in 12 games before tearing his ACL and missing San Francisco's postseason run to the Super Bowl. Last year, he began the season on the physically unable to perform list, returned to play in six games, but again ended up on injured reserve because of recurring issues with his knee.
He was the Giants' third-round draft choice in 2008, the 95th overall selection. In four years, he caught 160 passes for 2,315 yards and 18 touchdowns.
"Once a Giant, always a Giant. That's how I feel," he said Tuesday. "This is a very special place. I wanted to come back.
"I'm real excited. It's just great to see everybody, be around familiar faces, knowing everybody in the past and just being comfortable around everybody."
Manningham's best season with the Giants was in 2010, when he had career-high totals of 60 receptions for 944 yards and nine touchdowns. He had a career-long catch in each of the final two games, with an 85-yarder at Green Bay and a 92-yarder at Washington.
In the last three games of that season, Manningham caught 16 passes for 346 yards, a 21.6-yard average, and four touchdowns. In order, Manningham totaled 113, 132 and 101 yards to become the first Giants receiver with three consecutive 100-yard games since Homer Jones in 1968.
In his two seasons in San Francisco, Manningham played in 18 games with 13 starts and had 51 catches for 534 yards and one touchdown.
New York also signed free agent kick returner Trindon Holliday, who spent the last two seasons with Denver.
Holliday scored on a 105-yard kickoff return last season. He also had an 81-yard punt return against the Giants.
In a playoff loss to Baltimore two seasons ago, Holliday's record-setting performance saw him return a punt in the first quarter for a 90-yard touchdown, the longest punt return in postseason history. In the third quarter, he ran back a kickoff 104 yards for another score to become the first player in NFL history with a punt return touchdown and a kick return touchdown in the same postseason game.
At 5-foot-5 and 170 pounds, Holliday is one of the NFL's smallest players.
"Sometimes, I think my size is an advantage," Holliday said. "I can field the kicks and hide behind those big linemen when the other guys are coming down. It's hard for them to see me."