Harrell hit two free throws with eight seconds left to put visitors up 79-76 and Mason made two free throws with a second left to ice the victory.
With the win the Tigers evened their record at 11-11 and improved to 3-6 in the SEC. LSU dropped to 15-6 overall and 5-4 in the league.
“It feels so good to win, and win on the road,” said Harrell, who scored 28 points to go with 24 points from Mason. Cinmeon Bowers added his 13th double-double of the season with 16 points and 10 rebounds.
Harrell hit 7-12 field goals, 5-9 threes and 9-10 free throws on a night the Tigers made 9-20 treys, something Coach Bruce Pearl said his team would need to do to pull off the upset.
Mason hit 6-13 field goals, he was 3-4 on threes and 9-12 at the foul line with eight rebounds, four steals and three assists. He also played his best defensive game of the season.
“I think you gain experience from close games, but I think the most important thing we did this week was practice," Mason said. "We practiced situations for the last five minutes, and we play hard. We competed really hard in practice and I think that carried over into this game.
"We don’t let anything fluster us or anything like that," added Mason, a transfer from Niagara. "We kept together as a team and pushed forward.”
The head coach agreed with the guard. “The kids haven’t quit,” Pearl said. “They have got character, they have got heart. It is hard losing four in a row and then you have got to come in here. Tonight we represented Auburn.”
Auburn led for more than 32 minutes and virtually all of the second half, but LSU moved ahead 73-72 with 1:19 to play on a fastbreak basket by Tim Quarterman when Harrell lost control of the basketball.
The visitors responded with a perfectly run play as Mason passed inside for a layup by Bowers, who put Auburn up 74-73. Mason then got a steal and hit two free throws with 26.2 seconds left to make the score 76-73.
The Bayou Bengals cut the lead to one with a pair of free throws with 19 seconds left. Harrell then hit one of two free throws with 17.1 seconds remaining and LSU did the same thing with 11.5 seconds left.
Harrell got back to the foul line with eight seconds left and hit both of them to make the score 79-76. Josh Gray was fouled on purpose by Tajh Shamsid-Deen with 4.6 seconds left to prevent the home team from taking a three-point shot. He made his first and intentionally missed the second one.
After a scramble for the loose ball, Mason was called for a travel with 2.6 seconds left. However, Auburn defended the in-bounds pass with seven-foot-two Trayvon Reed blocking the passing lane. Mason came up with the loose ball, was fouled and nailed his free throws to wrap up the first road victory in eight tries this season.
Both teams shot well to open the game. Auburn took a 9-6 lead less than three minutes into the contest with Mason nailing a pair of treys following one by Harrell.
LSU’s biggest lead in the period was three points. Auburn built as much as an eight-point advantage at the 6:55 mark on a trey by Harrell to make the score 31-23.
LSU used its size advantage to cut the margin to 31-29 at halftime with a 16-10 edge in second-chance points in the first 20 minutes.
Halftime Numbers: Auburn built its two-point edge at intermission by hitting 6-12 three-pointers. Overall the Tigers hit 15-37 field goals for 40.9 percent. LSU made 16-35 (45 percent) from the field in the half with 3-9 on treys. LSU made 4-8 free throws while Auburn was 5-9.
Auburn was out-rebounded 25-21 at the break, but led for 13:51 in the first half thanks to 13 points from Harrell and 11 from Bowers.
Antoine Mason launches a three vs. LSU.
Auburn built the lead to 53-46 on a three by K.C. Ross-Miller with 14:26 in the second half, but LSU used its size advantage to outscore Auburn 24-13 in second chance points to tighten the game.
LSU pulled ahead 60-58 with 8:27 remaining, but Harrell immediately responded with a three-pointer and the Tigers kept their poise down the stretch.
“Several times when you look back we should have won games, but to finally actually do it and finish the game it feels great,” Harrell said. “Now we have to build on this.”
The visiting Tigers shot 42.6 percent from the field and made 20-27 free throws while LSU shot 43.9 percent while out-rebounding Auburn 45-38.
Pearl said the Tigers had to have a solid night shooting the ball to have a chance to win. “We aren’t the biggest team. We are the smallest team in the league, but we shoot the three ball pretty well. We have five guys that can shoot it so we try to have two or three out there and try to spread it.
"We had to make threes, take some charges and turn LSU over," the coach added. "That was a big key and we couldn’t let those guys have a big run up. I thought it was a great effort by our kids.”
Jordan Mickey paced LSU with 23 points, 12 rebounds and five shots while Quarterman scored 17 points. Jarrell Martin added 14 points and 16 rebounds for the Bayou Bengals.
“We wasted a great opportunity tonight," said LSU coach Johnny Jones, whose team is in the mix for an NCAA Tournament berth. "We played a team that had several losses in a row in conference. They came in and played desperately looking for an opportunity to win. They played with an edge.
"We allowed them to get comfortable out on the floor and make plays, execute, make shots and become a confident basketball team," he said. "With that, I thought we played too comfortable on the floor. Because of our comfort level, they became a very confident team.
"Unfortunately, throughout the game they led for 32 minutes," Jones pointed out. "Down the stretch, they executed and made the necessary plays that they needed to. Unfortunately, in this game, you can’t turn it on and off. You have to get it from start to finish, play every second of every play and have an edge about you. When you don’t, bad things are going to happen to you. We got treated to that tonight.”
Stat of the Game: Auburn’s defense limited the Bayou Bengals to 4-17 from three-point range while Auburn nailed 9-20.
Worth Noting: Auburn stole the ball 10 times while LSU had just three. AU outscored the home team 20-14 in points off of turnovers.
Up Next: Auburn will take on visiting Ole Miss at 5:30 p.m. on Saturday.