Following McNair's scramble, the Titans let the clock run down before calling a timeout, despite the length of the field goal attempt.
"I would have liked it closer, but it was a great gesture from him (Fisher) to have the confidence to keep it right there and let me kick it," Nedney said.
The Lions (0-5) had tied the game at 24-24 when Charlie Batch hit Desmond Howard with a 36-yard touchdown pass down the right sideline on a fourth-and-10 play with 1:18 left.
It was the second straight game-winning field goal for Nedney, who kicked a 49-yarder in overtime in last week's 31-28 victory over Tampa Bay.
Tennessee coach Jeff Fisher signed Nedney to a five-year, $6 million contract in the offseason after waiving veteran kicker Al Del Greco, who struggled last season.
Playing for his sixth NFL team in a six-year career, Nedney kicked three field goals in a listless first half, after which the Titans (2-3) trailed, 14-9.
"Playing in a dome is a beautiful thing, no wind or field conditions or anything like that," Nedney said.
Detroit appeared on its way to padding the lead early in the third quarter, but a 40-yard field goal attempt by Jason Hanson was blocked by Henry Ford and returned 69 yards for a touchdown by Donald Mitchell. McNair hit rookie Drew Bennett on a two-point conversion to give Tennessee a 17-14 advantage.
"There was a tackle coming in and there was a crease there," Ford said. "I got my hand on it. It kind of burned for a while, but I was just happy to make the play."
Detroit tied the game on a 23-yard field goal by Hanson with 9:38 left in the fourth quarter, capping a 14-play, 76-yard drive which lasted more than seven minutes.
But three-time Pro Bowl tight end Frank Wycheck starred on Tennessee's ensuing drive, catching passes of 21 and 29 yards before capping it with a six-yard touchdownthat gave Tennessee a 24-17 lead with 4:41 remaining.
Wycheck finished with seven receptions for a career-best 100 yards. The Titans have won nine straight against NFC teams.
"It was my turn today," Wycheck said. "He (McNair) made the throws up there to give you a chance. I just had to make the plays to help this team win."
The Titans have won nine straight against NFC teams.
"All I know is that wins are hard to come by for us this season, so we'll take it," Fisher said.
With Washington's overtime win over Carolina, Detroit is the lone winless team left in the NFL. The Lions are 0-5 for the first time since losing their first five games in 1989.
"For the most part I thought we contained McNair, but there at the end he popped out and made some big plays," Lions coach Marty Mornhinweg said. "There are a lot of great running quarterbacks and he's one of them."
McNair completed just 15 of 35 passes for 216 yards with two interceptions, but rushed for 48 yards on five carries.
Detroit stuffed running back Eddie George, who was held to 51 yards on 26 carries.
One week after throwing for a career-high 345 yards in a loss at Minnesota, Batch threw for 338 yards and three touchdowns.
Johnnie Morton recorded his third 100-yard game of the season with nine catches for 113 yards, including an 18-yard touchdown.
Batch also connected with Germane Crowell and Desmond Howard on scoring passes of 46 and 36 yards.
But Crowell, who had four catches on Sunday and 22 receptions for 289 yards this season, tore the patella tendon in his left knee and will be sidelined indefinitely.
After Nedney kicked field goals of 39 and 46 yards, the Lions defense came through with a big play. Linebacker Chris Claiborne intercepted a pass by McNair and returned it six yards to the Tennessee 26. Three plays later, Batch rolled to his right and hit Morton, who got behind rookie cornerback Andre Dyson, for an 18-yard touchdown with 2:14 left in the half.
Following a three-and-out by Tennessee, Crowell beat Dyson down the right sideline and caught a 46-yard touchdown with 1:30 remaining, giving the Lions 14 points in 1:16.
But a 50-yard pass from McNair to Bennett set up a 30-yard field goal by Nedney on the final play of the half.
Titans tackle Brad Hopkins and Lions defensive end Tracy Scroggins were ejected in the first quarter for swinging at each other after a play. Lions defensive tackle Luther Elliss was also ejected in the first half.