Manning threw three touchdown passes, including a momentum-grabbing 74-yarder to Cruz early, and the Giants claimed the final spot in the NFL playoffs, beating the Cowboys 31-14 on Sunday night to win the NFC East.
"I knew we were going to fight and keep playing until the end, I feel good about the way we're handling the ups and downs, and it comes down to finishing," Manning said after throwing for 346 yards and no interceptions.
New York (9-7) won three of its final four games for 65-year-old coach Tom Coughlin and earned a wild-card home game next Sunday against the Atlanta Falcons (10-6).
"We've had a lot of ups and down, but when our team needed it most we responded," said the up-and-coming Cruz, who has capped his team-record setting season with six catches for 178 yards. "We were able to keep level-headed when we were on the four-game skid."
The Cowboys (8-8) lost four of their final five games in their first full season under coach Jason Garrett.
Dallas was its own worst enemy with the season on the line. It missed tackles on all three of the Giants' three first-half touchdowns, failed to recover two fumbles within its grasp in the half and failed to convert on a Tony Romo sneak on fourth-and-1 at the Giants 10 while trailing 21-7.
"It's extremely painful and it's a damn shame," Cowboys owner Jerry Jones said. "We have a good team and I thought we would be going to the playoffs, but that didn't happen. We have to be able to take some of the good with the bad and move on. We did a lot of good things this year, but to point to one thing why this happened would be subjective. We're 8-8 and we have to be better than that."
Romo, who played with a bruised right hand, moved the Cowboys in the second half but all he could generate were touchdown passes of 34 and six yards to Laurent Robinson.
"You can't make excuses,' said Romo, who finished 29 of 37 for 289 yards and one interception. "Either you win or you go home. Give them credit for coming in here and being ready. This is not going to sit well with me or anyone else on this team. It should fuel the fire to come back, but right now, it hurts."
The shorter touchdown pass to Robinson got Dallas within a 21-14 with 10:15 to play, but Cruz, the second-year pro from nearby Paterson who has become a fan favourite with a big plays and salsa celebrations, came through again.
Cruz boxed-out cornerback Orlando Scandrick on 44-yard third-down jump-ball catch and caught another for 20 yards to set up a 28-yard Lawrence Tynes' field goal. Manning iced the game with a four-yard TD pass to Hakeem Nicks with 3:41 to play.
Manning finished 24 of 33 as the Giants beat the Cowboys for the second time in four games and ended a regular season marked by inconsistency on a high note. Cruz, who set a single-season record for yards receiving, averaged 29.7 yards on the night, and of course, he did his touchdown salsa after the first score.
"He's unbelievable," Giants guard Chris Snee said. "He's so explosive. He's so quick, he just runs away from people. He unbelievable. I don't know what else to say about the guy."
The Giants defence sacked Romo six times, including twice by Osi Umenyiora who returned to the lineup for the first time since spraining an ankle late last month. Dallas' final possession ended with Romo being sacked by Justin Tuck and losing a fumble.
"We needed this win," Umenyiora said. "This is the biggest win we've been a part of for a while."
The Giants haven't won a playoff game since beating the-then unbeaten New England Patriots in the Super Bowl in 2008, and the one thing that is seemingly apparent is that this team is peaking.
Coming off a 29-14 win over the rival Jets last week in what might have been the Giants best game of the season, Coughlin's team put together another outstanding 30 minutes in jumping to a 21-0 halftime lead.
Cruz, who sparked the win over the Jets' with a team-record 99-yard touchdown, made another monster play on the Giants' second offensive series, turning a short pass into points.
Cruz caught a short square out, eluded a tackle by Terence Newman, turned the corner after getting a seal block from Nicks and outraced two defenders down the sideline in front of the Giants bench for a 7-0 lead.
Dallas went three-and-out but had a chance to get right back into the game when Will Blackmon muffed a punt at near his 30-yard line and Alan Ball failed to recover.
Manning made Dallas pay. Manning hit Nicks for 18 yards and Devin Thomas for 14 en route on a 68-yard yard drive that Bradshaw capped with his five-yard run. Safety Abram Elam had a chance to tackle Bradshaw in the backfield and Bradshaw scooted into the end zone after he missed.
Manning had passes of 14 and 12 yards to rookie fullback Henry Hynoski in an 80-yard touchdown drive just before the half. Bradshaw, who had a 29-yard run early in the drive, broke a tackle by linebacker Bradie James in scoring on a 10-yard swing pass for a 21-0 lead.
The Giants had chances to put the game away in the third quarter. They moved to the Dallas 42 on the opening possession of the second half and elected to punt.
Romo then drove the Cowboys 94 yards with a no-huddle offence, hitting Robinson on a 34-yard go pattern down the right sideline on a play that cornerback Corey Webster was beaten.
An interception by safety Antrel Rolle gave New York the ball in Dallas territory but they failed to convert a fourth-and-1 at the Dallas 35 and the Cowboys came right back to cut the deficit to seven.
Notes: Cowboys G Kyle Kosier left the game with a knee injury and was replaced by Kevin Kowalski replaced him. ...Cowboys LB DeMarcus Ware had 1 1/2 sacks and finished the season with 19 1/2. ...LB Sean Lee led the Cowboys with 11 tackles. ...LB Mike Boley had nine for the Giants. ...New York's other sacks were registered by Jason Pierre-Paul (16 1/2), LB Jacquian Williams, Tuck and Chris Canty. ...Dallas was limited to 49 yards rushing on 16 carries.