Favre also connected on a 4-yard touchdown pass to wide receiver Donald Driver in the third quarter and a 10-yard pass for a score to running back Ahman Green in the fourth quarter that gave the Packers a 31-21 lead.
"We needed a win a lot more than I needed 400 touchdown passes," the three-time MVP said.
The Packers (2-1) almost lost a grip on the game late in the fourth quarter when Green fumbled the ball away in Detroit's 26. Lions cornerback Jamar Fletcher recovered the ball and was tackled from behind by tight end Bubba Franks on the Lions' 32.
Lions quarterback Jon Kitna moved Detroit to Green Bay's 45 on a 19-yard pass to wide receiver Roy Williams with 11 seconds remaining in the game. But Kitna's Hail Mary pass into the end zone on the final play of the game was batted away by a group of defenders, sending the Lions to 0-3.
"Like I told our team, that's the way you're supposed to play football on Sunday afternoons," said McCarthy, who was doused by Gatorade by fullback William Henderson at the end of the game. "It was a great victory for our football team. It gives us something to grow with and I'm very proud of our guys."
Green was held to 63 yards rushing on 22 attempts as the Packers struggled to rush the football. He led the Packers with a team-high eight catches for 68 yards. But Favre, following a solid performance in a loss to the New Orleans Saints last Sunday, completed 25 of 36 passes to 10 different receivers for a season-high passer rating of 127.1 and no interceptions.
Kitna passed for 342 yards as the Lions piled up 424 total yards of offense, but Packers safety Marquand Manuel picked off a pass that bounced off ex-Packers receiver Corey Bradford late in the first quarter and returned it 29 yards for a touchdown, giving Green Bay a 14-7 lead.
Kitna's main target was wide receiver Roy Williams, who finished the game with single-game career high 138 yards on 7 catches (19.7 avg.), including 42-yarder from Kitna on the final play of the first quarter to tie the game at 14-14. It was Williams' fifth career 100-yard receiving game, and his 19.7 yards per catch average was the highest of his career in games where he has recorded at least five receptions.
The Packers, a 6 1/2-point underdog, beat the Lions for just the sixth time in the last 15 regular season games with Favre as quarterback in Michigan.
Jennings, who played at Western Michigan University in Kalamazoo, finished with three catches for 101 yards receiving, the most by a Packers rookie since Sterling Sharpe had 137 (on seven catches), Sept. 25, 1988, vs. Chicago at Lambeau Field. Billy Howton holds the team's single-game rookie record, 200 yards (on six catches), Dec. 7, 1952, at the Los Angeles Rams.
"I think we got confidence now, especially with a bunch of young guys on the team," said Driver, who finished with 3 catches for 20 yards. "We got our first win against a division team, a rival team, so it gives us something to build on."