Ten teams entered the NFL's final slate of games battling for four playoff berths.
With all four NFC division titles up for grabs in Week 17, the Panthers were first to clinch, overtaking the Falcons when quarterback Cam Newton hit Greg Olsen with a seven-yard touchdown pass late in the third quarter for a 21-17 lead.
The Panthers (12-4) were made to sweat as Atlanta (4-12) mounted a last-ditch drive with less than a minute to go in hopes of a game-winning field goal but after reaching their own 43-yard line, a bad snap led to a 16-yard loss and Carolina held on for victory.
Carolina, advancing to the playoffs for the first time in five years, also earned a first-round bye.
They set a franchise record with nine sacks of Falcons quarterback Matt Ryan, including four by defensive end Greg Hardy.
Four teams had been vying for the sixth and last playoff spot available in the AFC, but the Super Bowl champion Baltimore Ravens and Miami Dolphins squandered their chances, leaving the door open for San Diego and Pittsburgh.
The Ravens (8-8) lost 34-17 on the road against the AFC North champion Cincinnati Bengals (11-5), while the Dolphins (8-8) fell 20-7 to the visiting New York Jets (8-8).
Pittsburgh did their job, powering past the Cleveland Browns 20-7 to improve their mark to 8-8, making San Diego's clash against the Kansas City Chiefs decisive.
A win by the Chargers (8-7) over the playoff-bound Chiefs (11-4), who have already secured a wildcard berth, would give them the spot. A San Diego loss would put Pittsburgh in.
The Seattle Seahawks (12-3) were in line to clinch the NFC West and homefield advantage throughout the playoffs provided they beat the St. Louis Rams (7-8).
The other two NFC division championships will be fought over in head-to-head showdowns later on Sunday.
The Chicago Bears (8-7) were hosting the Green Bay Packers (7-7-1), who were welcoming back quarterback Aaron Rodgers after a seven-game absence due to a broken collarbone, with the winner claiming the NFC North crown.
The Philadelphia Eagles (9-6) were visiting the Dallas Cowboys (8-7), with Kyle Orton starting at quarterback in place of the injured Tony Romo in Sunday night's closing contest with the victor taking the NFC East title.
The New Orleans Saints (10-5) were looking to clinch a playoff berth with a win over Tampa Bay (4-11). A Saints loss, however, would give the Arizona Cardinals (10-5) the opportunity to advance with a victory over playoff-bound 49ers (11-4).
In other early games, quarterback Andrew Luck and kicker Adam Vinatieri registered record-book entries as AFC South champion Indianapolis Colts beat the Jacksonville Jaguars 30-10.
Luck completed 26 of 37 passes for 282 yards in becoming the first player in NFL history to top 8,000 yards for his first two seasons.
Vinatieri kicked three field goals and three extra points to move into fifth place on the NFL career scoring list with 2,006 points, passing George Blanda and Matt Stover.