Etienne scored on a 28-yard run in the second quarter, but it was his 1-yard plunge with 3:05 remaining that preserved Clemson's third consecutive victory over the Seminoles.
The victory delivered a third consecutive Atlantic Division title and third straight ticket to the ACC Championship Game in Charlotte, where the Tigers (9-1, 7-1) will play ACC Coastal Division champion Miami on Dec. 2 at Bank of America Stadium.
Clemson appeared to be in command against for much of the game against the Seminoles (3-6, 3-5), leading 17-0 late in the third quarter. But Florida State made it interesting, scoring two touchdowns in a seven-minute span to cut the Tigers' lead to 17-14 with 8:53 left.
Quarterback James Blackman drove the Seminoles 90 yards in seven plays to set up a 3-yard run by freshman running back Cam Akers, then found tight end Ryan Izzo wide open for a 60-yard touchdown.
The Seminoles appeared as if they might pull the upset when Clemson quarterback Kelly Bryant fumbled the ball with 6:54 remaining on his own 39-yard line, but Clemson safety Van Smith intercepted Blackman on the next play and returned the ball to the Seminoles' 44.
Six plays later Etienne bulled his way in from the 1 to give Clemson some breathing room with a 24-14 lead with 3:05 left.
Running back Adam Choice added a 10-yard run with 35 seconds left for the final score.
Clemson's defense dominated over the first 30 minutes, with five tackles for loss, including four sacks, five passes broken up and two forced fumbles. The Tigers held the Seminoles to 46 total yards and three first downs in the first half and also set the table for Clemson's first score.
Linebacker Tre Lamar sacked Blackman for a 12-yard loss and recovered Blackman's fumble on the play, setting the Tigers up at the Seminoles' 20-yard line.
Clemson scored six plays later on a 2-yard run by Bryant, his 10th rushing touchdown of the season, with 2:51 left in the first quarter.
Ray-Ray McCloud set up Clemson's second touchdown with a 35-yard punt return to the Seminoles' 28. Etienne dashed 28 yards up the middle on the next play for his eighth touchdown of the season with 6:34 left in the first half.
Clemson extended its lead to 17-0 with 1:33 left in the half on a 26-yard field goal by Austin Spence.
NOTES: Clemson WR Ray-Ray McCloud ranks 13th in the nation in punt returns with a 13.5 average. ... WR Deon Cain has caught at least one pass in 33 consecutive games, the 10th longest active streak in the nation. ... Florida State RB Cam Akers is the first Seminoles running back have two 50-yard touchdown runs in one game (Syracuse) since Chris Thompson in 2012. ... DE Josh Sweat had two tackles for loss, including a sack, against Clemson, giving him 12.5 this season to topping his career high of 11.5 set in 2016.